Search found 109 matches

by DavidG
Sun Apr 02, 2023 4:30 pm
Forum: Solar Scope Modifications
Topic: Any feed-back on remote control for tilt-tuned filters ?
Replies: 24
Views: 3072

Re: Any feed-back on remote control for tilt-tuned filters ?

For the stepper motor control you might want to consider the MyFocuser system by Robert Brown. It was developed for controlling a focuser remotely for astrophotography but the operation would work perfectly for this application as well. It is very easy to build has many option like temperature compe...
by DavidG
Tue Feb 07, 2023 3:55 pm
Forum: Solar Scope Modifications
Topic: Etalon PST problem - NEWS
Replies: 51
Views: 6259

Re: Etalon PST problem - NEWS

On my PST's ( I have two ) the Teflon ring that comes in contact with the upper surface of the Etalon is on a slight angle. So it doesn't make contact evenly. So to reduce any possibility of tilting you might consider placing your silicon ring above the Etalon so the Etalon is against a hard surface...
by DavidG
Mon Feb 06, 2023 2:34 pm
Forum: Solar Scope Modifications
Topic: Etalon PST problem - NEWS
Replies: 51
Views: 6259

Re: Etalon PST problem - NEWS

Bob, If you own a PST all you have to do is look down at the Etalon as you turn the ring and you easily see it tilting and as we know tilting is easy way to tune them Valery's statement using a laser is again showing that the Etalon is tilting and that is mechanism of how it is tuned If you wanted t...
by DavidG
Sun Feb 05, 2023 3:08 pm
Forum: Solar Scope Modifications
Topic: Etalon PST problem - NEWS
Replies: 51
Views: 6259

Re: Etalon PST problem - NEWS

I'm sorry but the Etalon in a PST is a simple tilt tune mechanism and not pressure tuned by mechanical force applied to deform the Etalon. The patent is red herring about pressure tuning by applying force to the Etalon. It is not used in a PST. The end of the tuning ring is machined on a slight angl...
by DavidG
Sun Feb 05, 2023 2:26 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Maier ITF replacement
Replies: 4
Views: 1174

Re: Maier ITF replacement

Nope. Chris provides the 0 ring because the active area of his filters is slight smaller then the original so it is to prevent any light leaks. On of the keys to making these filters last is to seal them against O2 and water. So the coatings are not applied out it the very edge like the original Mea...
by DavidG
Mon Jan 16, 2023 2:51 pm
Forum: Solar Scope Modifications
Topic: Repairing a CaK PST
Replies: 45
Views: 10873

Re: Repairing a CaK PST

Alexandra,
Yes that is the Maier's filter I'm using.

- Dave
by DavidG
Sun Jan 15, 2023 11:24 pm
Forum: Solar Scope Modifications
Topic: Repairing a CaK PST
Replies: 45
Views: 10873

Re: Repairing a CaK PST

Hi All, Happy 2023 ! I finally had both some free time and clear skies to use my repaired CaK PST that I used a Maier Photonics filter to replace the bad one in mine. Visually today I could see the CaK features and was very pleased with the images it was producing with my ZWO 120 monochrome camera. ...
by DavidG
Wed Nov 02, 2022 4:15 pm
Forum: Solar Scope Modifications
Topic: Repairing a CaK PST
Replies: 45
Views: 10873

Re: Repairing a CaK PST

Alexandra,
I have not imaged through my CaK with the new filter but it is on my list and will post images when I do. I can say that the image is much bright and I see it visually pretty well and even see some CaK features on the disk when I cover my head with dark cloth.

- Dave
by DavidG
Wed Nov 02, 2022 4:11 pm
Forum: Solar Scope Modifications
Topic: Repairing a CaK PST
Replies: 45
Views: 10873

Re: Repairing a CaK PST

Bob, Here is what is listed on Maier's site for his 393 filter that I used 393 Bandpass Filter - sulfur line gas chromatography Center wavelength=393 nm +/- 2 nm Bandwidth=13 nm +/- 2 nm Size=12.0 mm dia. x 5.0 mm thick Out of band blocking > optical density 4.0 (xray to 2000 nm) Coating type= Non h...
by DavidG
Sat Oct 22, 2022 2:44 pm
Forum: Solar Scope Modifications
Topic: Repairing a CaK PST
Replies: 45
Views: 10873

Re: Repairing a CaK PST

Like others that own a CaK PST, the filters will hazy over with age. So far the main yellow one in the OTA is still in good shape but the blocking filter in the eyepiece tube had hazied over. I took it into work and measured it. It was only passing less than 2% at the CaK wavelength . I was still ab...
by DavidG
Tue Apr 10, 2018 10:01 pm
Forum: Solar Scope Modifications
Topic: Maier ITF - first failure?!
Replies: 12
Views: 5807

Re: Maier ITF - first failure?!

Both of my Maiers filters are still perfectly clear and my two are the first two he made.

- Dave
by DavidG
Wed Feb 22, 2017 9:18 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

With it being 24 years old the odds are very good that it has drifted off the CWL of 656 and is also cloudy. It should look perfectly clear so if you see any hazy it has problems.

- Dave
by DavidG
Wed Feb 22, 2017 4:34 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

Have you checked the narrow band filter ? If your unit is 10 years old then the filter might have aged and is no longer on band.

- Dave
by DavidG
Thu Feb 16, 2017 3:21 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

You can assembly the unit minus the narrow band filter and see if you can get an eyepiece to focus of the edge of the cone. Since the Moon is about the same diameter as the Sun you can try the unit out again without the narrow band filter in place to see if you can get the Moon and the occulting con...
by DavidG
Wed Feb 15, 2017 3:16 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

The key is that H2 that contains the Iris is located at the aperture stop of the system So V2 might not be in the correct position. Here is a link to my math that shows how to calculate the spacing for all the elements in a solar coronagraph. http://considine.net/dgroski/promscope/prom3.gif so you c...
by DavidG
Tue Feb 14, 2017 10:51 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

The main parts should be the tube with the lens and occulting disk, with the occulting disk facing the focuser of the telescope. Next, what screws on the back of that tube ( end without the lens/disk) is the tube with the iris, and screwed on to that is the tube with the second lens without the disk...
by DavidG
Tue Feb 14, 2017 3:53 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Baader Halpha Coronagraph (prominence viewer)
Replies: 21
Views: 9652

Re: Baader Halpha Coronagraph (prominence viewer)

Hi, Having designed and built coronagraphs from scratch I'll be happy to try to happy. http://considine.net/dgroski/promscope/ The first issue you might have are the occulting cones. The diameter is determined by the size of the solar disk produced by the telescope. The Sun's disk is approximately 1...
by DavidG
Mon Aug 31, 2015 8:25 pm
Forum: Solar Scope Modifications
Topic: I have a PST (40mm)... Need to clean scope
Replies: 5
Views: 2517

Re: I have a PST (40mm)... Need to clean scope

A Q-tip that is only slight damp with isopropyl alcohol can be used to clean the surface of the filters without any damage. It is possible that the spot your seeing are on the ITF filter and the coating are known to go bad. The ITF filter is not the small 5mm that you see when you remove the eyepiec...
by DavidG
Sat Aug 22, 2015 4:07 pm
Forum: Solar Scope Modifications
Topic: Etalon reconnecting, Success !!!
Replies: 5
Views: 2724

Etalon reconnecting, Success !!!

Last weekend I was in Vermont at the 80th Stellafane convention. Stellafane has a legendary Swap meet on Saturday morning and you'll never know what you'll find. In the piles of treasures was a PST that the owner stated gave a sharp image but the Etalon needed adjusting since his kids had dropped it...
by DavidG
Sun Apr 13, 2014 3:30 pm
Forum: Solar Scope Modifications
Topic: What is it and for what is it to use ?
Replies: 8
Views: 1651

Re: What is it and for what is it to use ?

Walter,
I think it is some type of artifical star. Light is reflected off the big mirror onto the little mirror, then back off the big mirror and then brightly illuminates the pin hole.

- Dave
by DavidG
Sat Apr 12, 2014 8:46 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, You need to do the final alignment on a defocused star. You most likely only need to adjust the primary in the "M" plane so the primary mirror is tilted a little bit more away from the secondary. Remember to recenter the star in the eyepiece after each adjustment. - Dave
by DavidG
Sat Apr 12, 2014 8:35 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, modding an old SPV
Replies: 4
Views: 1516

Re: Appenzellersun, modding an old SPV

Walter, You might consider this filter from Omega on Ebay. It is cheaper then the Andover filter and narrower in bandwidth. - Dave http://www.ebay.com/itm/Optical-Interference-Filter-656-3-H-Alpha-0-15nm-Band-Pass-Double-Pass-/310516117756?pt=Educational_Toys_US&hash=item484c33f0fc#ht_1173wt_1074
by DavidG
Tue Apr 08, 2014 8:30 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Hi David step four done. I'm not far of the 62.5 mm depending on where I hold the ruler on. Looking up the tube I see nothing but the primary. I wonder how that looks on the moon ;-) . I guess I have to wait a couple of days. the laser still points to the middle of the primary give or take a Millim...
by DavidG
Tue Apr 08, 2014 5:58 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, Excellent alignment so far. You just need to tilt the primary away from the secondary so it is no longer is visible in the when you look up the focuser. In your picture, showing what you see when looking up the tube, your at Step 3 in my drawing. The primary mirror is looking at the secondar...
by DavidG
Tue Apr 08, 2014 1:51 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, When the primary is aligned correctly, the laser being reflected off it should be around 62.5mm (125/2) from the edge of the secondary. It may be much more depending on the design. So if you taped a piece of paper off the back of the secondary mirror cell you can use that as a target to alig...
by DavidG
Mon Apr 07, 2014 8:18 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, I added more information to your picture. Once you tilt the primary so the laser spot falls back on the center of the secondary you should be able to move the primary in the plane shown by the red lines and the laser should hit the spot marked as red dots. If you continue to increase the til...
by DavidG
Mon Apr 07, 2014 5:53 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, In your picture looking up the focuser I can still see the edge of the tube so your primary mirror is still not adjusted correctly. It looks to me that your primary is both out of adjustment in the plane that the mirrors moves when you turn the screws for the "M" plane and also the...
by DavidG
Sun Apr 06, 2014 9:24 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, When you look up the focuser, the only thing you should see is the primary mirror and with nothing in it. If your seeing part of the tube or the secondary mirror then the tilt of the primary is not great enough. Here are some pictures that show what you should see when you use the laser and ...
by DavidG
Thu Apr 03, 2014 6:49 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, Here is how I align my Schief using a laser collimator 1) Place the laser collimator in the focuser 2) Adjust the tip and tilt of the focuser so the laser beam hits the center of the secondary 3) Adjust the the tip and tilt of the secondary so the laser beam hits the center of the primary 4)...
by DavidG
Thu Apr 03, 2014 1:24 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, first light in the hand, Schiefspiegler/Kutt
Replies: 41
Views: 7793

Re: Appenzellersun, first light in the hand, Schiefspiegler/

Walter, If you have any questions on the optical performance, or collimation I maybe able to help. I'm the designer of the Delmarva Schief in which I improved the optical performance over the Kutter design. We also have Yahoo Group for 'SchiefBuilders' https://groups.yahoo.com/neo/groups/schiefbuild...
by DavidG
Tue Apr 01, 2014 6:31 pm
Forum: Solar Scope Modifications
Topic: Reducing Spherical Aberration In Our Scope Mods
Replies: 45
Views: 9021

Re: Reducing Spherical Aberration In Our Scope Mods

It is actually very simple to test a lens for spherical aberration at any wavelength you want ie check for spherochromatism. You setup the lens a double pass autocollimation mode us an optical flat. Since we are taking about small lenses, a good quality flat optics are available for not much money. ...
by DavidG
Tue Feb 18, 2014 12:58 am
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in mainten

Hi Joe,
Thanks for jogging my memory about the Helio vs Ceolostat. I should have remembered the difference since I 'm restoring an original Hale spectrohelioscope that uses a Ceolostat.

- Dave
by DavidG
Mon Feb 17, 2014 5:19 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in mainten

Hi Walter,
I'm interested in the clock drive. The two brass gears attached to the clock look to give a ratio of 1:1 so that means the clock motor itself needs to turning at 1 revolution in 48 hours to track the Sun. Have you measured it's speed ?


- Dave
by DavidG
Mon Feb 17, 2014 2:24 am
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in mainten

Hi Walter,
I think what the symbols mean is that if the Sun is drifting downward then you want to move the slow motion control in the direction the arrow is pointing to recenter the image.


- Dave
by DavidG
Mon Feb 03, 2014 10:35 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Walter, The light source ( your lamp) and the reflection off the mirror were it comes to sharp focus must be next to each other and you need to move them as unit until the reflection comes to a sharp focus. Please see the website I provide a link to. Think of it this way, when a you look at a star t...
by DavidG
Mon Feb 03, 2014 10:34 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Walter, The light source ( your lamp) and the reflection off the mirror were it comes to sharp focus must be next to each other and you need to move them as unit until the reflection comes to a sharp focus. Please see the website I provide a link to. Think of it this way, when a you look at a star t...
by DavidG
Mon Feb 03, 2014 8:11 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Walter, I'll assume that the 4.045 meters is 1/2 the distance you measured to were the reflection of the lamp was in sharp focus. You should have measured 8360mm and 1/2 of that being the focal length or 4180mm. Most likely why you did not measure the 8360mm distance is that you need to place a scre...
by DavidG
Sun Feb 02, 2014 11:27 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Walter, The simplest method to find the focal length of the primary mirror is to use the Sun and measure the distance from the surface of mirror to the were the image comes to sharp focus. Since the mirror is both uncoated and also has a long focal length, there is no danger of catching anything on ...
by DavidG
Sun Feb 02, 2014 8:44 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Walter, It looks like the writing on the back of the primary mirror is "R= 8360". If this is the case that usually means the the Radius of Curvature is 8360mm and the focal length will be 1/2 of this or 4180mm. So the primary mirror needs to be this distance away from the focuser or the im...
by DavidG
Sun Feb 02, 2014 8:36 pm
Forum: Solar Scope Modifications
Topic: Appenzellersun, Polar Coelostat arrived , now in maintenance
Replies: 47
Views: 7853

Re: Appenzellersun, Polar Coelostat arrived , now in maintenance

Hi Walter, Very nice instrument. It is a version of Gerrish mount like the one built by my good friend Jim Daley http://stellafane.org/tm/tg/daley2/daley2.html With the primary mirror having a 8 meter focal length and what looks like a 120mm aperture, it is most likely not a parabola but a sphere si...
by DavidG
Mon Jan 27, 2014 10:08 pm
Forum: Solar Scope Modifications
Topic: Hello, new user and looking for a way to repair my BF15
Replies: 10
Views: 2362

Re: Hello, new user and looking for a way to repair my BF15

If your ITF is the same as a PST then Maier Photonics makes a replacement. I used one to repair my rusted ITF in my PST. http://maierphotonics.com/656bandpassfilter.aspx

- Dave
by DavidG
Fri Jan 10, 2014 6:26 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

I've 1 question : why this solution would be better than the one from Beloptik that is already existing?
If you referring to a PST, those are not a direct drop in replacement for the original ITF and the cost is higher.

- Dave
by DavidG
Thu Jan 02, 2014 4:37 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

Hi Mark,
Thanks for posting the plots. What I find interesting is that these plots show that the total transmission at 656nm is 45% for a Coronado ITF, while the Maier filter is 70%. So in theory if all else was same the Maiers filter should provide a brighter image.

- Dave
by DavidG
Mon Dec 30, 2013 5:20 am
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

Hi Steve, The edges of all your filters, were there is no coating are clear so that shows the coatings were applied to a clear substrate and not the RG630 glass. The red color could be from a number of sources. It could be a coating that was applied on purpose, it could be from the ITF coatings or i...
by DavidG
Sun Dec 29, 2013 11:05 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

By the way the "edge blackening" shown on the filters is the epoxy seal that stops the filter from "Rusting". If it is not there then the life of the filter is GREATLY reduced. I wouldn't be surprised if the filter didn't last a year. That is real poor of Meade to let a filter be...
by DavidG
Sun Dec 29, 2013 10:56 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

Steve, Your picture clearly show that both your BF-15 and rusted PST ITFs are using clear glass as the substrate just like Mark's BF-10 ITF. So that is the difference of why the Maier's filter is causing the dimming when used in the Solar Max system. Mystery solved ! This is first I have seen a PST ...
by DavidG
Sun Dec 29, 2013 9:44 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

Steve, Your rusted ITF from your PST must be different then what is being used now in them. It is possible that it is ITF from BF diagonal ? All the ITFs I have seen that have come out of a PST are combination of two filter systems. The ITF layer is used to block IR, these layer is deposited on red...
by DavidG
Sun Dec 29, 2013 5:20 pm
Forum: Solar Scope Modifications
Topic: Front end replacement ERF for new "blue" PST??
Replies: 108
Views: 13498

Re: Front end replacement ERF for new "blue" PST??

Steve, The Maiers ITF was designed for a PST and not the BF5. diagonal. The transmission characterist of the BF-5 diagonal when matched with the SM-40 Etalon are different, and this why the image is dim. When I used the filter in my PST the image is bright and much brighter then my rusted ITF. As sp...
by DavidG
Sat Dec 28, 2013 8:42 pm
Forum: Solar Scope Modifications
Topic: Simple Improvement for CaK PST
Replies: 4
Views: 1223

Simple Improvement for CaK PST

After the success of replacing the ITF on H-alpha PST with the Maier Photonics unit, I decide to take a look at the filters in my CaK PST. It never gave a bright image and it seem to be getting a little dimmer. I found that the blocking filter which is located at the very bottom of the focuser tube...
by DavidG
Tue Dec 24, 2013 6:08 pm
Forum: Solar Scope Modifications
Topic: Latest PST different?????????
Replies: 29
Views: 4324

Re: Latest PST different?????????

On the original PST version the rubber grip ring and metal ring under it was attached to the Etalon tilt mechanism by a small screw. It looks this has been replacemnt by a screw that extends outside the scope and is used as a lever to still tilt the Etalon. So 95% of the scope is the same. I know on...