jetstream

Yes too many things to try at once can make things interesting in the wrong direction. Now I need a Petzval! Btw in the linked thread mirror reflectivity was discussed- Celestron is most likely telling the truth about the 85% IMHO. In talks with a top coater and optician it came to light that reflectivity specs are "nominal" and can vary across the surface a bit. The best coaters get 95%-96% and the best mass produced mirrors about 92%-93%, both subject to variation. The best ones have less variation. Not a frac topic but interesting-and might apply to lens coatings. My 90 SV is extremely sharp and with lower transmission than the TSA120.

I could use my (chrome) head as an artificial star to collimate then?!

Do you have a reducer? Talking NV is like walking on thin ice

Ok I knew that 😄 Just makin sure you did

Can you explain Jeremy?

I'm waiting for the TC Fonemate... I am very interested in seeing actual whole system MTF,extremely interested. Distance is from the calculator as discussed Vlaiv?

Funny you mention NV- this might be part of the re org but where I live in Canada makes buying things challenging ie shipping costs, customs costs etc etc. Way off topic and anyone feel free to boot me from the thread for it- I've wondered how an SCT with the f2 would work? too narrow fov? My 90mm Raptor f7 is on deck in the meantime.

As a member of "people kind" maybe "people kind up?"😃

Great choices! I have found that (for me) every little bit from 90mm up to 120mm-130mm makes a very nice difference. From here I like to go to 200mm on up, with 250mm being a great all round aperture. I looked at the APM LZOS but at the time it seemed as if availability was going to be an issue according to Marcus. I drool over those lenses. Then TEC didn't reply to enquiries on a 140mm and so Tak was chosen (once a supplier was found-that was the issue). Almost bought the TOA130 but very heavy and quite a bit more. I found buying a good frac here to be challenging. Truly happy with the Tak I have. Eagerly waiting reports with the APM!

@Deadlake- what scopes do you have? just curious and sorry if you posted the answer already. I'm reorganizing the line up here.

I thought about it but there are few things that work in these temps- my dobs no issue- the fracs stay in the house.A bunch of eyepieces are needed so that when eye moisture/heat frosts them up, you get the next one. I cherry pick the best cold weather eyepieces-only used the 21APM,17/14 Nikon HW and the 18mm ES 82 last night. The ES are perhaps the best in the cold. The Zeiss zoom for lunar/planetary gets the nod as well. I tested the advertisings claim from years ago about water...so I took my 30mm ES 82, frosted up in sub -30c temps and threw it in warm water in the sink... That was many years ago and the eyepiece is like new. The ES just might be the toughest eyepieces out there IMHO.

Did you find out how much?

I use 1piece wool long johns, 2 layer track pants,a thick hoodie then 1 piece snowmobile suit bibs followed by the snowmobile jacket. The one piecers help trap heat in. A very thin balaclava is a must and is surprising how well they work with a leather/fur bomber hat sitting there for use as needed. Good insulated boots-Baffins- with thick socks. Its my hands that take a beating in the cold- those aluminum eyepieces will cause close to frostbite in a short time.

Please tell me you don't have one of these too!! I can't keep up!

Its -36c no wind this morning which I'll take over last nights observing session -31c with 20k+ wind gusts. Its the wind that will cut you in half. IMHO.

Tonight is bitterly cold,-32c with the wind gusting to about 20kmh- well below -40c wind considered. Thats the bad news, the good news is the sky- super transparent and dark. Years ago @ollypenrice posted an image in a thread about the "finger" in M42 and I hope its ok to use his image. The 15" was pulled out of the seacan, collimated and set in the sun for a few hours to ensure no frost on the primary, and it worked. If I pull the scope out at night, the mirror can cause issues, temp dependent. The goto eyepiece for this was the Nikon HW 17mm/EIC for 14mm. Surprisingly the Finger appeared straight away with 2 very faint stars above it and one off the end, brighter. Orientation is the view through the eyepiece. It extended over from the "hook" or notch in the wing and down a bit. Confirmed! I should have noticed this before and I look forward to more detail tomorrow night with the 24" at f4.1. The Flaming Star was a showpiece tonight as well as the colour in M42, mottled green core with light salmon pink under the wings. More observed but not too much. At least I lasted an hour out there observing! Those wind gusts will cut you right in half...

Hey Mike, would you still talk to me if I bought one of those new Takyhashi reflectors? A Mewlon 250CRS?😃

This might be why- from Astro Physics https://www.astro-physics.com/254f145mc "The optical design follows the original concept of aspheric primary with secondary spot on the inside of the corrector . The simplicity of this 2-element optical system assures no collimation issues - the scope will always retain collimation and cannot be knocked out of alignment because there is no secondary mirror to fuss or adjust. The small 23% central obstruction assures the highest possible planetary contrast at high powers. This obstruction also acts as a baffle to keep stray light from the sky from falling directly on the eyepiece. For high-power eyepieces, a 23% obstruction is enough to fully shield the field of view from this stray light. When the field of view exceeds about 1 inch diameter, light from the sky can leak past the front baffle and reduce the contrast at the edge of the field. Therefore, for low-power, wide-field viewing with 2” eyepieces we provide a larger secondary baffle that will increase the front baffle size to 32% to block this stray light in the outer portions of the field. This is needed primarily when sky light-pollution is high and you are using low-power wide-field eyepieces to observe faint deep-sky objects. Under dark skies, there will be no difference in contrast. Note: this secondary baffle threads onto the front of the corrector. The photo does not show the method of attachment on the corrector."

Yes, Im surprised too- I saw this in the pictures. A 23% obstructed Mak with good optics would be perfect IMHO. Thanks for this information. A 10% reduction in CO would be considered a huge improvement.

@Captain MagentaExcellent Magnus, missed this thread unfortunately. What did you end up figuring the central obstruction was in the end? for the 180mm

Hi Mike! Why does your signature say Antares 1/30 secondary?😀

Thanks for all the info Stu, it is stored and being processed in a very cold mind! (-52c with wind this morning)

Hi James, I thought it might be enlightening to discuss collimation (and also cooldown) because these 2 issues can really mess with the views visually (and imaging).It can boil down to "getting a good one" possibly. I would take a C8 with "better" optics (a "good one" ) that is collimated tighltly over a C9.25 that is mediocre any day. Of course a "good"C925 would be preferred if size and weight is not an issue. I mentioned the Edge because if miscollimation appears or is there to start with, it has a very easily removable sec and with easy corrector adjustment should the sec need to be moved a bit to line up (not tilt). Maks might have a longer cooldown and the SW Maks baffle might up the CO to about 30% from 23%. They are reputed to be sharp scopes if you can cool them.

Actually these are really nice scopes, and I have a question- how would the cool down compare between the 8"Edge vs the C9.25? One more- is there a difference with regard to seeing? I'm looking at the C8Edge for imaging as well as visual. I'm also going to buy the Hotech SCT collimator as I can't stand the thought of collimating one of these with a star. The Edge series looks much more flexible with regard to precise collimation. Realistically though these scopes most likely hold collimation very well, I kinda got a twitch of OCD with regards to it however.

a what?! an SCT?!! and with lovely views? just how does it compare to a ,well lets see...hmmm, how about a 100mm refractor on the moon?