Special H-Alpha Doublets Optimized for Solar Works

[Ales - iStar Optical]

Hello guys,
recently we received more than half dosen of requests to design and produce a special doublets optimized for H-Alpha imaging and visual works. Since most lenses on the market are designed to work perfectly in RGB but neglect the H-Alpha wavelength, which is normally not so important when it comes to a "well working" achromatic or R30 anastigmatic doublet. Those of you who want to have a truly great doublet for imaging in H-Alpha must live with the common doublet (suffering from some nasty aberrations incl. astigmatism, spherical aberration, etc..) or shop around and try to find a company which is able to design and produce a single lens down to customer's specs (like Istar). But such one time production lenses are very expensive. So we came up with an idea to produce a range of specialized, optimized doublets designed for H-Alpha imaging. I was wondering how many of you would seriously consider purchase of such highly specialized lens suitable solely for the Solar works. I was thinking of 127 F8, 150 F8 and 180 F8 and possibly 228 F8. Prices of these would be comparable to our R30 lenses, possibly a little less. Let me know, paricipate actively, post similar questions on CN since I cn not do this as a vendor.
cheers,
Ales

[borispider]

We do have a well know imager in our club who is on a Solar kick right now.
He uses 80mmEd scope(I believe) right now w/filter on the front and a solar
diagonal. I don't know any of the details but Mike might.
With all the Solar imaging going on at CN I think you might have a market for it.

[Ales - iStar Optical]

Personally I was also surprized to see how many people are involved in Solar imaging. So the decision was already made, we will produce first H-alpha lenses by end of this summer. We will start with 150 F8. Also, to the line up mentioned below we will ad one 204 F9
best regards,
Ales

[Ales - iStar Optical]

Just a quick note about our progress. Recently we received a number of requests for an H-Alpha 220 to 228mm lenses in F7 to F10 range. A special request was made from one Italian private observatory, one US private observatory and the Hohenkarpfen observatory in Germany. After talking to each one of them, we agreed on producing the SAME lens for all three places, 236mm lens diameter, 228mm clear aperture F/9 made of short flint and special crown, optimized for H-Alpha wavelength with maximized resolution. We are just about one with the optical design and we will produce first three lenses in about 3 month time. If you want to jump on this oportunity, let us know, a 50 percent down payment of 2100 US dollars will put you on a very short production order list and you can get your new, professional H-Alpha lens with 9" of clear unobstructed aperture before Christmas. Talk to Mike Harden about your order or any other H-Alpha lens you may need.
Secondly, we are finished with the 150 F10 H-Alpha lens, the price will be announced soon and we will ad these new H-alpha lenses on our web site. Stay in touch, I will keep you informed,
cheers,
Ales
ISTAR Optical

[pbsastro]

Ales,
I would guess that more than 90% of the people that would use these scopes will use the 4x Baader/telecentric unit. As the goal is usually to achieve f/30 or above, the ideal base f/ratio is f/8 which gives f/32. F/7 giving f/28 is still acceptable for someone with size constrains.
Going f/10 and longer will not bring much benefit regarding the filter bandwidth and will make the scope not transportable in a regular car, which is a big no. At least for me it is. Even the 150 f/10 is completely ruled out for me because it is not transportable.
Additionally the larger ERF Baader sells from stock is 180mm. Larger sizes may be available on special order, but will have a very high cost and the wait will be very long.
So a 7" f/8 scope seems to me the ideal scope. It matches the Baader 4x telecentric and 180 ERF, and is also the larger size transportable in a regular car. 1400mm is really the limit to fit in the back seat or in a regular trunck.

If you make one 7"f/8 count me as a guaranteed sale. Only request is that it is exactly 1400mm (not 1420 or 1440) to binoscope with my 175/f8 apo.

One question, why do you call it F30 in your web site? Do they have extended color correction when used as regular scope compared to a standard achro also optimized for H-alpha?

Pedro

[jpb30]

Hello Alès

where is the construction of my 228 H-Alpha, Always planned before noel ?
i begin to make the plans for the tube of the 228mm OTA, can you give me the external diameter of the cell ?