Ideas for ultra-compact telescope?

[Chandra]

11 hours ago, Oscar23 said:

Re: anti-CA filters, I have some helpful material for comparison...

Good contribution. The Baader Contrast Booster seems to be the winner in this comparison... It would undoubtedly be the most economical option for our OP, and, furthermore, there would be no customs problems with it... In any case he also wanted to improve its support and, preferably, expand the aperture to 5", so the use of a CA control filter in his current scope would probably not meet his expectations...

[Tiny Clanger]

12 hours ago, Oscar23 said:

Re: anti-CA filters, I have some helpful material for comparison...

 

It would be polite to state the sources of the material, crediting Gary Parkerson and Wolfgang Rohr at the very least. I note the copyright symbol the latter has added to his photos, so it should not be reproduced, just linked to.

[Louis D]

I've tried a bunch of filter combinations to reduce CA on my 152mm achromat and ST80.  The Baader Semi-APO helps a bit to remove the majority of the violet while not disturbing the color balance too much.  It does this by utilizing a 450 to 460 nm light yellow filter to block some violet on a Neodymium substrate that blocks the yellow-orange part of the visible spectrum to compensate for the excess yellow.

The best, cheap compromise I've found is a 470 nm long pass (yellow) filter that I picked up from a commercial filter supplier.  It is stronger than the typical astro Yellow #8 (~450 nm LP) and weaker than the Baader 495 LP.  A photographic Yellow #8 is roughly a 480 nm LP filter, and would be my second recommendation.  It's a bit too strong, but much less objectionable than the 495 LP or a Yellow #12 which is about a 510 nm LP.  They are available in 48mm sizes which fit 2" eyepieces or diagonals perfectly.

The more vexing problem is how to cut unfocused red at the other end of the spectrum once the unfocused violet is truncated.  This requires a cyan or short pass (SP) filter, which are only available from commercial filter suppliers.  I've found a 625 nm SP to be about the best compromise.  Thus, a 470 nm LP stacked with a 625 nm SP is about the best I've found for making fast achromats usable for high power work.

[JOC]

On 08/05/2024 at 21:42, happy-kat said:

If you are handy at making things you could make a dobsonian base at home for a telescope

That ^^^ was also my thought when I read the enquiry, but OTA's for larger Dobs are not that small even flex-tubes like mine.

Mind you unless the OP wants the light grabbing potential of a larger mirror to go chasing feint fuzzy's I also wondered if they could make as much progress improving what they have?  The reviews I read on the scope suggest that the OTA/Optics are quite useable, but let down by the mount.  Would the OP be better off spending their cash and load allowance on a better folding tripod for it, for example a good heavy duty camera tripod.  I own a Manfrotto 055 (MT055XPRO3 2nd hand off MPB if you get that chance) that looks to me well up to taking a telescope and would fold to go into a tall rucksack (and I bet the others on here will have better suggestions).  It must be possible to buy a top mounting arrangement that would take the existing scope and maybe invest in 3 nice EP's to go with it, possibly a better focuser if it is changeable.  

[Tony Acorn]

5 hours ago, JOC said:

That ^^^ was also my thought when I read the enquiry, but OTA's for larger Dobs are not that small even flex-tubes like mine.

Mind you unless the OP wants the light grabbing potential of a larger mirror to go chasing feint fuzzy's I also wondered if they could make as much progress improving what they have?  The reviews I read on the scope suggest that the OTA/Optics are quite useable, but let down by the mount.  Would the OP be better off spending their cash and load allowance on a better folding tripod for it, for example a good heavy duty camera tripod.  I own a Manfrotto 055 (MT055XPRO3 2nd hand off MPB if you get that chance) that looks to me well up to taking a telescope and would fold to go into a tall rucksack (and I bet the others on here will have better suggestions).  It must be possible to buy a top mounting arrangement that would take the existing scope and maybe invest in 3 nice EP's to go with it, possibly a better focuser if it is changeable.  

I too have a s/h Manfrotto 055 that I bought with Manfrotto's matching gear head and the pair cost me £150 IIRC. It is a rock solid combination that I use for a range of photography, sometimes with a Star Adventurer 2i wifi Pro bundle for astro work. I've just bought an "open box" StellaMyra 80mm ED f/6.25 from our sponsors to go with that pairing as a portable astro rig - once delivered, I'll let you know how well it is all suited.

[alacant]

On 08/05/2024 at 20:58, Buqibu said:

TableTop Dobsonian

Hi

This one. Lovely little thing. Bright. No false colour. Backpack-able. 130mm.

HTH

 

Edited June 6 by alacant

[AdityaR]

On 09/05/2024 at 00:28, Buqibu said:

... Celestron Astromaster 102AZ...

Anything would be upgrade over it tbh. If you are talking visually...I'd say go for a Nexstar 5SE and if you want to do AP too with minimal effort get a ZWO SeeStar(but you can't use it visually, i think) or you can get. If your sole purpose is AP, then you can get a WO Zenithstar 73 APO or a WO RedCat 51 APO (that is, if you have a Good GoTo EQ Mount and DSLR for it)..

Edited June 8 by AdityaR
Forgot to add some more suggestions.