jetstream

It doesnt matter to me where we talk about it- up to you I have 6 good deep sky filters... 1 Older Astronomik OIII- good but a bit wide. 2 Older Lumicon OIII- excellent 3 Older Lumicon UHC -excellent 4 NEW Televue OIII (made by Astronomik) the best OIII Ill probably ever own 5 NEW Televue Nebustar (UHC type) excellent +, but it seems wider than Lumicon but shows more-maybe higher transmission? top notch 6 DGM NPB-very good- but did I just get a good sample? As you can see if I was going to buy a new filter it would be the NEW Televue, followed by the Astronomik. The Nebustar, made by Astronomik deletes red. I would click the mouse, buy to take advantage of the skies IMHO. Edit: John just reminded me with his post-I also have a top tier Astronomik Hb 1.25"-excellent and my least used filter so 7 filters.

Make the right choice- I didnt twice- and got ripped off.

If you beg, borrow or steal (kidding) an OIII the list is long from your skies. Pacman in Cass, Monkeyhead and Rosette in Gemini plus a bunch of fainter ones -Jellyfish etc etc. they are all over the place.

@Deadlake thanks, perfect. I'm at the point now where I'm just going to use what I have scope wise but plan for imaging as well. i called about getting the TV adapters here- zero idea when i can get them. I could get the NV shortly. I want to make sure though to avoid a costly mistake. The TSA120 will be used for lunar imaging, visual and NV. Sure glad I got it. I'm also sure your gonna love that APM LZOS.

@John I wonder if your method helps with the WTF function more than the MTF ?!😃

No idea about Petzvals but I did look at Televues 101, 127. Just so many scopes out there... I think with modern coatings the air spaced triplets rival the oil spaced but no doubt this could spark debate. check out Astro Physics site under support for grat info including thermal shock. Ok now I want a Petzval lol! actually I'm looking at NV specs now too... there a CDN company I wonder if its good GSCI

I think that one technique used by experienced astronomers is to "sort" through scopes to find "good" ones regardless of test reports 😃 or lack of.

I was going to sell the 90mmSV for a "faster" telescope, imaging wise. Many thanks to @vlaiv for the patience and information regarding sampling rate- I will now try this scope for widefield DSO imaging down the road. I think Long Perng makes good glass.Yes, I think APM had to do something to reduce sample to sample variation, just my humble opinion.

@Deadlake you guys are lucky to have FLO as a vendor. Stellarvue, in the past sorted through (Chinese?) lenses and then star tested them to ensure performance -and it worked very well IMHO. Now they use interferometers etc and still star test. Williams optics use similar glass (top notch) I think so they should be VG- and any issue is most likely through the assembly process IMHO. If the glass itself was poor I think any vendor would change the line up. interesting that APM released some doublets years ago with interesting performance. No links but if I remember CN had posts about it. You can rest assured the LZOS lensed scope will be superb.The MTF (and everything else) will be near perfect.

@Nikodemuzzhttps://www.baader-planetarium.com/en/blog/apochromatic-triplet-objective-why-oil-spaced-lenses/ "Oil-spaced lenses by TEC, Astro Physics and Baader: do not have to be protected from leaking oil. Horizontal storage is no problem, either. You only have to avoid temperature shocks. Never carry such an expensive instrument from the freezing cold outside at eg. -25°C into your cozy living room – this would mean a temperature difference of 50°C in a couple of minutes! But temperature differences of 25°C didn't cause any problems in tests over long periods of time. We are using a cool chamber in our production facilities to test dome parts, motors, circuit boards – and even lenses – at a temperature of -86°C to reliability of operation and perfect function under extreme conditions. Oil leakage is one of the few problems which can rarely affect lenses by Zeiss, Astro-Physics, TEC or by us – but only if they were mistreated. Here at Baader Planetarium, we have experienced opticians who have completed a multi-year training at Carl Zeiss Jena. We repair such oil leakages of lenses by Astro Physics/TEC and Zeiss since more than 20 years – quick and easy. So we think that the advantages of oil-spaced"

Not sure but most likely not from what I hear-just coffee shop talk though.Same goes for scope vendors I think... this device could be a nightmare for them IMHO.Company 7 tests all the optics they sell and if I remember could have been at odds with some manufacturers. This is a good company. I could get the poor ones refigured but there is that deal about residual strain in the glass..between shipping and preliminary testing I could go in the hole.

Years ago I talked to Astro Physics and wanted to buy a scope- they are excellent to talk to- but didn't want to wait years for one. I was advised against the oil spaced lenses for hard fast cooling. "Lens shock". I think the oil can leak out. I tried to find info to post but can't find it. Maybe check the Company 7 web site. I enquired about a TEC but no response. I would still own an oil spaced refractor but wouldn't risk using it in the extreme cold.This is another plus for the TSA120-air spaced.

Of course the Shack Hartman device opens up the possibility of buying a bunch of GSO mirrors (16"), testing them and keeping the good ones for the truss dobs.Some of them are really good I hear, but... then theres the rest. Moreso for the secondaries... I would weed these out too.

If were talking refractor triplets-yes. Re: lens cell vs -30c 1. Some scopes cool down successfully at times, not always like my SVRT90 and SW120ED. The SV has had more succesful cooldowns. 2. My Tak 120 so far has cooled successfully every time, no astg from cell distortion/pinched optics. There is a zero guarantee they will all work like this 3. Avoid oil spaced triplets for cold temps- its very hard on them.IMHO 4. Once a successful cooldown happens its my experience the scope will be fine, no aberrations. 5. Keep trying and if a succesful cooldown happens just keep the scope near ambient. ie my 90mm SV is ready to go, in the seacan at -30c today. These are just my thoughts on this.

Holy cow! about 17% Strehl on the first scope... this is what Im interested in- the whole system capability. Well, I was tossing around buying out a dob maker, too complicated here in Canada but I do have his support as well as from a top optician who loves testing optics and supporting the astro community.I'm sure I could be helped along with the flats as well as set up, my numbers, the results etc, to get me going. The main question would be-would it pay for itself? Dreams are nice but then there is reality. Thanks for the info Andrew.

I wonder if the the test results from one would be held in high regard? I'd buy one if I could test a few scopes to pay for it and I could have my own fracs tested by an optician I know, for comparison and reference with regards to accuracy. The exchange rate is in the wrong direction for me... Does this set up do mirrors?

Ok wait a minute if I turn the image with the mentioned feature "up" its not doing this is it? 🖕 😀 It must be cold I'm surfing emojis lol!

The mechanics on this scope are junk IMHO. It would take to much work to fix. The upside? I have plans down the road to build a carbon fibre, high spec newt with as small a CO that will fully illuminate the field.

Yes, please! and user friendly 😀

Yes, I see that after leaving UK years ago they continued the linguistic legend!

I just happen to have a 200mm f3.8 (with a broken focuser)!

I have to say that as a Canuck who watched English comedies from very young, Monty Python, Ronnies, Some mothers do have em etc that there is no better comedy or command of the English language than you guys have! Budgie Smugglers!!lol! man I'm laughing at this one after looking it up and am "chuffed to bits" that I found the meaning 😀 My hat is off to you guys 👍 and I still watch English comedy at every chance. (but no more sci fi )

I thought about the f4.1 too... but I'm becoming ceased up a bit here with OA and that monster is a challenge - not sure if the Doc is on board with it after the operation(s). Funny how fast things can change.

Excellent! I wish you better luck in acquisition than me Vlaiv. I have a long list of dreams atm (camera, etc etc) with no hope in site.

I used to but then grew up