All crown/flint achromatic doublets will suffer from some degree of CA, depending on refractive index.



https://en.wikipedia.org/wiki/Flint_glass

I think the ST80's refractive index will give it a bit more CA than the 102mm Meade as it is faster. I use the Baader Semi-Apo on the ST80 but I also have the Fringe Killer and the Contrast Booster. I think the Neodymium will make a difference on the ST80 depending on what you're looking at.



You could always substitute a Wratten yellow contrast filter to act as a minus cyan filter.



The #8 and #12 were often used for this purpose I believe.



Above you can see the Baader Contrast Booster (left) compared to a TS Optics (GSO) Wratten #8 filter.

 

I've not used the Baader 495, although I believe it's not unlike a Wratten #12. I think you can alternate between the two (#8 and Baader 495) and see which works with the prevailing conditions, target etc. For most DSO's you may not need them at all, especially if you use the UHC-S.

You might find this conversation interesting at Rowdy Fights: http://www.cloudynights.com/topic/472024-baader-495-longpass-filter-with-st80/

 

Yeah they should work. I think the Semi-Apo gives the most natural view and the Contrast Booster is probably closer to the Baader 495. The Semi-Apo is like the Fringe Killer and Neodymium combined. If you stack the #8 with the Neodymium it's probably very close to what the Semi-Apo does anyway.

The UHC-S is best for diffuse, planetary and/or emission nebulae, like M42. It has a 97% transmission but with the ST80 I'd probably stick to around a 3mm exit pupil depending on target and conditions. It took a 40mm Plossl for 32.5x and a 3.1mm exit pupil on the 102mm Skymax.

With the Bazooka I could get 64x for a 2mm exit pupil with a 14mm (Baader Morpheus) plus UHC-S on a number of DSO's. M42 and M20 were particularly good I thought this year.

The ST80 was pretty good with a 16mm T5 Nagler on M42 with the UHC-S (25x). Theoretically, with the ST80, the UHC-S would work best with eyepieces at 15mm and longer. Although I wouldn't totally rule out a good 10mm eyepiece (or Barlowed equivalent) for a 2mm exit pupil (40x) in the right conditions.

Like I've always maintained, as the aperture gets smaller using any type of ultra high contrast filter gets increasingly more difficult. It would be interesting to try the UHC-S on the Skymax with a reducer.

 

I can help you find the 'common-thread' for the great optics that have poured out of Japan for many decades: CARTON OPTICAL INDUSTRIES, LTD

Carton has made the lenses, and some complete telescopes too, for almost every great telescopes we have been using, Unitron being the very tip of the ol' iceberg. It was 'Putanedo Patrick' from Chile (UK originally) who sent me chasing down this intel. Thanks, Pat! Here's a brief Pdf. on the scopes, etc. made by Carton:

Carton Optical Company.pdf

And there's a Yahoo Group for Carton Optical, too:

https://groups.yahoo.com/neo/groups/cartonscopeclub/info

I wish I knew this info long ago - I'd have picked up quite a few years ago, at rock-bottom prices. Even my first 'big' telescope - an Edscorp (Edmund Scientific) 3" F/15 achromatic refractor in 1972. It had the same lenses as the 3" Unitron! And there I was, pining-away at not being able to afford that Unitron, while sitting right next to my 3" Edscorp! Ouch!

Good to hear that Standing Rock is being paid it's due attention over there. I just heard this also from a dear Little 'ol Lady-friend of mine in Yorkshire, Janet. I taught her about our philosophies. She taught this to her friends over there. And now there's a Sioux enclave in Yorkshire! Ask me to tell you my story of the Mohawk-War I was in. Or Big Mountain.

So here's a couple of photo's of a Carton scope. Check out the Yahoo-group. There's some fascinating stuff there!

'Ta

Dave

 

Thanks for the info about Carton Dave. Speaking of optics, I christened the Baadertron last night with M41 and M42 inter alia. Although the 19mm Panoptic was in the diagonal most of the time as usual.



And, as usual, the clouds soon came to spoil my fun.






Baadertron evolution lol.

 

Well, I have had a mixed day. I've managed to find an Astrozap dew heater that will fit the Skymax and I've ordered it and a Moon book.



The Skymax is good on the Moon and the book should compliment my decades old Rukl Moon Atlas nicely (why is Rukl out of print now?). I may even get to use my bino and the Vixen mount with it. Either way I can get an easy 236x out of the Skymax. Talking of the Skymax, the new TS Optics reducer has arrived. It could give the Skymax f/6.3 which may give it a bit more range. Although I plan to use the ST80 for DSO/MO's.



So far it seems OK. I can't detect any grainy sensation whilst threading it into anything like with the [expletive deleted] Antares reducer.



From daylight testing on a 90mm Mak it seems more or less the same as the [obscene hand gesture deleted] Antares reducer. Except of course the thread seems normal. Only time will tell I suppose to see if it ends up like the [foaming at the mouth, crazed ranting and all reference to forcing the said Antares product into any human orifice deleted] Antares reducer.

Oh yeah, TS Optics are sending the chocolate teapot back to me as they reckon it's now 'repaired'.

 

Honestly .... you couldn't make this stuff up.

 

I'd check Amazon carefully for that book as there are some pretty crazy prices for it.



I paid about 23 quid for mine, where they get the figure of £164.78 from I don't know. Not sure whether mine's a hardback or not yet but I definitely wouldn't pay over £25 - 30. My tablet just b'lerked to tell me that the chocolate teapot will arrive Wednesday. Wunderbar. At least the tripod will come in useful as the Bazooka's has weathered a bit being left out over the summer.



I can use the teapot's slo mo controls as the Bazooka's have rusted slightly. The tray will fit the Vixen if I need a spare.



It's these plastic guides at the bottom of the tripod that have split. The tripod can still be used in its lowest position but you can't safely raise it anymore.

You're right about mobility and observing. I bit off a bit more than I could chew with the Big Cat but I'm positive I'll be able to assemble it in the Spring when the weather's better. The ST80 and 102mm Skymax will both be much more easy to use quickly. The reason I initially bought the 102mm/4" Skymax was that with its OTA diameter of 12cm exactly I could pick it up with one hand. The ST80 is beautifully light and compact of course. The Mak has the slight advantage for lunar/planetary and no CA, while the ST80 is ideal for DSO's. If my maths is right I may get a 2.3° TFOV with a 30mm Vixen NPL (21.6x) and the 0.5x reducer on the Skymax. Although to be honest I don't see it having any real advantage over the ST80 for DSO's.

The ST80 will give about 3.2° with the TV T5 16mm Nagler and the 19mm Panoptic. An 8mm Plossl should give exactly 1° TFOV for 50x. My 10mm Baader Eudiascopic should give around a 1.1° TFOV. A 20mm Plossl will give 2.5° TFOV. As a comparison the Full Moon is about 30 arc minutes (29′20″ ~ 34′6″) in angular diameter (I think lol).

My head hurts now ...

 

Looks like I can get it for under a quid lol! Probably an old library book.



I just found this old screenshot from last year's solar eclipse. Some solar viewing gear would have come in handy then! I think that was my old Belnea laptop before it borked itself into the twilight zone. It ran Ubuntu 14.04 LTS well after running Vista 'The Pants OS' for seven years. It would probably be still going now but the trackpad broke.



The book on the right is worth looking out for second hand. It's basically Antonin Rukl's Moon Atlas. I don't think Rukl's Moon Atlas is in print anymore, not in this version (Hamlyn) anyway.

 

Hmmm.....

So you now have a 0.5X focal-reducer, eh Mak? TS-store-brand. It should work fine. FR's aren't rocket-science, and the Antares was the sole anomaly I've ever seen! And oh boy - was that ever a good one! I hope you don't wind-up with PTSD over that!

I've seen 'stupid' before though. Meade used to make the 2" FR 03.3X for the SCT's out & about. But hundreds of people complained bitterly to Meade that they made everything vignetted and fuzzy. So Meade did the only thing they could think of to remedy this: They simply removed them from the marketplace! But they didn't truly address the issue:

The people complaing about them were all trying to use them visually. So of course they vignetted and fuzzed everything! They were made for imaging only! But Meade didn't think to add a simple caveat to their advertising: NOT FOR VISUAL USE! How's that for 'stupid?'

Now the Meade 3.3X FR's command a handsome price in the 'used' marketplace. If you can find one. I bought one just before they were withdrawn by the Einstein's of Meade Instruments of Irvine, California. But this vacuum in the market was soon filled with new entries in the 3.3X, mostly in the well-recieved 1.25" size. I have the $249.00 model - with utterly fantastic clarity and coatings - made by Rock Mallin of MallinCam-fame. Nice guy! He helped me track down the origins of a bizarre FR I have in my stable of FR's. Image below:

Optec MAXfield 0.33X Three Element Telecompressor -



Note the infra-red filter.




These were the quite rare Optec MAXfield 3.3X Telecompressor. The cam it's attached to is the MallinCam PRO Junior. The Optec came from AstroVid in New York - gone now. They made the venerable, and highly regarded, StellaCam II and StellaCam III. Many believe these were and remain the finest monochrome B&W video-cams of all time. That's mine below:



Video-AP: Leave your telescope outside and let IT freeze - stay indoors, warm, and watch the show on your screen!

Brrrr...

Dave

 

Video astronomy looks interesting, but expensive lol. The TSO reducer looks fine so far, I'm pretty sure it's GSO as TS rebrand a lot of their stuff.

 

The BAA have been going since the 19th century. I've often wondered about joining but it's about 50 quid per annum, which is roughly half a TV Plossl lol!

https://britastro.org/