My latest, H-alpha, PST mod set-up for a 6" f/10..

Frankenscope? Let's see it!***be advised that NOTHING in this forum has been safety tested and you are reading and using these posts at your own peril. blah, blah, blah... dont mess around with your eyesight when it comes to solar astronomy. Use appropriate filtration at all times...
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My latest, H-alpha, PST mod set-up for a 6" f/10..

Post by Rusted » Sun Sep 20, 2020 2:18 pm

Rather than continue hijacking Jack's thread about protective filters I have added my own details here.
Thanks to Merlin's advice I am moving the protective filters up the light cone. I have achieved 100mm spacing in front of the etalon but have more M48 extenders on order. You need M48 male/female, filter threaded extenders. NOT 2" sliding fit extensions.

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Here are some images of my dedicated 6" H-alpha solar telescope. Not to show off but to help other builders, like myself, when I was starting out in H-alpha.

It took some time to establish a reliable, non-sagging, H-alpha, etalon and filter train for my home made H-alpha scope. I now use a full aperture Baader D-ERF in front of the objective instead of an internal, sub aperture 90mm D-ERF. I saved money with the 90mm D-ERF but eventually fried my ZWO camera! Not much of a saving! :roll:

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There was a detour into T2 fittings which proved too weak for the cantilevered loads. Eventually I settled on a cheap, 2" long throw, helical focuser. This works well with the cheap DC motor focusing. I often need to re-focus when changing GPCs [three and without, makes four different options.]

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Then the blocking filters each have their own power. So they need refocusing too when I make a change. I use the Lunt B1200 almost exclusively for surface detail. The PST BF is better for proms. The B1200 stops far more light than the PST BF. So needs far more gain to expose the dim proms. Gain just masks the proms with noise. So is best avoided.

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After some practice with a secondhand 6" F/8, I now use an iStar, H-a, 150mm f/10. 1500mm focal length x GPC power means I need to avoid touching the telescope. I use compact, 1.25" TS GPCs rather than Barlows. Otherwise the very long focal length, up to 3m with a GPC fitted, easily throws the sun out of the field of view. So the belt driven motor focus is well worth having. I made a PST etalon, belt drive too. However, I needed to manually tilt the exposed etalon, as well as turn the tuning ring. I may repack the etalon to see if it helps.

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For the main tube I use a straight seamed, 160mm Ø, factory ventilation, galvanized steel, extractor duct. The seam is aligned with the gap at the thumb wheel [clamping point] in "Skywatcher," hinged, tube rings. The straight seamed tube is much prettier IMO than the much more common spiral ducting. It is of very thin steel and so weighs much the same as a thicker, aluminium tube. These straight seamed tubes are intended for dusty factories. Where a duct fire in a spiral tube is a very serious risk. I was lucky and found a stock of scrap tubes at a local furniture factory. The tubes come in roughly 4" to 16" diameters, perhaps even bigger.

I turned the massive back plate in two piece on my old lathe. It helps to balance the heavy iStar objective in its cell. Particularly when such a long and heavy, cantilevered, filter stack is attached. A normal focuser is best avoided as it changes the fixed etalon position in the focused beam. [200 mm inside focus.]

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I am only really interested in capturing close-ups of solar features. There is far too much competition for perfect whole disk images from highly skilled and experienced imagers. So I found myself a niche which [initially] didn't cost me the huge fortune of buying a commercial 6" solar telescope. I made my own large mounting too. So that saved about $15k.

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It still wasn't cheap to set it all up but I spend most sunny hours in my DIY observatory trying to capture what I can see. So the cost per hour is dropping like a stone. Meanwhile I am investing literally hundreds of hours in practicing my strange pastime. Being retired means that I spend more time in a day than many hobbyists can manage in a whole month, or more. I like to think that I am making slow progress by endless iteration of all my mistakes. ;)

"What do I do for a hobby? I take deep red, black and white, close-up pictures, of the Sun." :D


http://fullerscopes.blogspot.dk/

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, Assorted TS GPCs, ZWO ASI174.

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