AR2403

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AR2403
Taken by Bill Hrudey on August 26, 2015 @ Cayman Islands

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AR2403 is difficult to resist - it can become an obsession. The first w/l image was with a 5X Barlow and, the second a 3X Barlow. The H1a images are for completeness lest this mode be forgotten. TS 115 mm APO triplet with Baader wedge for the w/l images and, Lunt 60DSPT for the H1a. Captured with DMK41 and SharpCap 2.6; processing with Registax 6 and PSP7. East/West not reversed. Best viewed in the enlarged window with dark background.

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Comments

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Very good work my friend !
I think that with the first image you have reached the maximum with a 115mm. Now you need go to a 204mm ;-)
Cheers,
Bernard.

Posted by astrofrenchy 2015-08-26 17:14:02

Hi Bernard;

Yes, I was thinking the same thing - youre right. With all my experimenting with my TS 115 mm thus far, I do believe Ive reached its Dawes limit. Not sure I want something as large as the Istar though. May give some thought to a SCT with Baader solar filter or, equivalent.

Liked you lunar image the other day - I appreciate the difficulty in even tone over an object with HDR.

Cheers,

Bill

Posted by whrudey 2015-08-26 17:27:51

Hummm...SCT? Youll always have a central obstruction which decreases the quality, not as in a refractor. For the Sun you dont need an APO, just a good achro or anastigmat lens as you are working in a narrow band of the light.
Cheers,
Bernard.

Posted by astrofrenchy 2015-08-26 17:44:14

True - my understanding is that, given equal quality optics, the two key variables are lens diameter and focal length. Lens diameter for Dawes limit and, focal length for primary magnification rather than adding Barlows which can have compromising effects on resolution. If I remember correctly, I once saw a w/l image by Alan Friedman using a 10 inch Mak/Cass: http://www.avertedimagination.com/img_pages/maelstrom.html looked pretty good to me.

I will watch out for a good 6 inch, or larger, achromatic lens and, with my trusty machine shop, I could easily manufacture the rest. Just another item on my long list of things to do.

Cheers,

Bill

Posted by whrudey 2015-08-26 18:33:16

This is super. How much would a setup to shoot this quality cost ... ball park figure. Ive been toying with the idea of purchasing a Meade 8 or 10 inch catadioptric. Would that work ... with the proper accessories?

Posted by Zircon 2015-08-26 19:01:14

UPDATE re: Resolution:

Hi Bernard & Zircon;

I crunched some numbers regarding Dawes limit. My 115 mm refractor reaches 1.008695 arc sec and, the 8 inch Istar reaches .571429 arc sec. Thus, the ratio of 1.008695 by .0571429 equals 1.7652 times better resolution with the Istar. On comparing your images with mine, I think this is in the ball park.

A 10 inch SCT (I dont think there is a difference between mirror or lens) could resolve .456693 arc sec. One could not use the Baader wedge with a SCT - rather a glass or film solar filter at the front which, may compromise image quality a bit.

Regarding Zircons question as to cost, a 10 inch SCT on a wedged fork mount (cannot use the LightSwitch series as they have only one arm) would cost north of U$2000 plus the solar filter which may add another U$2-300.

Hope the above is useful. I would be interested in any feedback.

Cheers,

Bill

Posted by whrudey 2015-08-26 19:43:17

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