John

Give it a try and see if it makes any difference. Nothing to loose as it's already installed

Well I tried it a few times but found that using it didn't seem to make any noticeable difference either to the cool down time or the performance when cooled My primary mirror back is quite exposed though - it's one of the older Orion Optics primary cells. Maybe that helps with cooling ? Quite a small fan as well.

My first "proper" telescope was an Astro Systems 6 inch F/6. I used it to observe Halleys Comet

I think mine works off a PP3 battery. I don't use it though.

So far Mark, I've found it pretty tough to split with my Tak 100mm if the seeing is not top notch (an apt term where double stars are concerned !). With the ED120 and 130mm triplet the split is somewhat easier. At 1.1 arc seconds the tighter pair are very close if not on the resolution limit with 100mm of aperture.

Nice report Mark I'm glad you enjoyed Tegmine - it's become a favourite of mine this season

Light pollution has been changing over the last few years with the introduction of LED lighting and the phasing out of the older sodium lights. I believe that the older ones could be filtered to some extent but the newer lighting not so much ? For galaxies there are no filters that help really. Darker skies are what is required to see them better. The O-III and UHC filters do help with nebulae. They work even better under dark skies of course but with some light pollution at least something can be seen with them.

If you go for and SLT or a Nexstar this website is a mine of information on them. The SLT scopes are covered in the "Odds and Ends" section: https://www.nexstarsite.com/index.html

I have an Aero ED 30. It's a nice eyepiece at F/7.5 and even F/6.5 but is not as well corrected as the 35mm or 40mm in the Aero ED series as scopes get faster. I've not used the Vixen you mention so I can't comment on that one.

The seeing was OK last night but there were just too many clouds about. I had a nice view of Venus with the ED120, split Tegmine again, got Iota Leonis and Castor and then gave up cloud doging. More clouds than clear patches. It was supposed to clear later but at 12:30 am it was no better so the scope came back it. Fortunately there are more clear nights forecast over the coming 7 days. Maybe a bit of rain tomorrow will clear the air ? 20% chance of that tomorrow evening according to the forecast.

It is forecast to get clearer as the night wears on but I'm probably not going to stick it out. There are some decent nights forecast over the next 7 days with the moon rising in the early hours so hopefully darker skies for DSOs.

It's not called "The Realm of the Galaxies" for nothing ! Hope you get a decent result Blooming clouds are really annoying here tonight - just get the scope on something and then it's gone

I found that I needed that beta version to get it to run.

The ED doublets I've owned and used have all been a step up from achromatic doublets, obviously in terms of CA control but also in terms of SA correction and therefore high power definition. It seems to me that when the more expensive glass is used the manufacturers take a little more care with figuring and polishing.

I'm only commenting on the optical tube but, personally I feel that the C5's are a bit more versitle than the 127 mak-cassegrains (which I've also owned) but there is not a lot in it. But I can't tell you if the versatility is worth £200 to you.

Fair enough - it was just an example. I don't think the 25mm would justify the £400 in all honesty. I've had a few 5 inch Celestron SCT's and found them pretty capable little scopes. Not into GOTO myself so I don't have any opinions on that.

Thanks Alan. Good to know they are there even if they are beyond most of us. Mag 14.7 is as faint as I've got with my 12 inch scope from home so I may have a shout at the mag 14.9 one if a really good night comes along. At least it is in a relatively bright galaxy !

The additional 25mm of aperture is the difference. £400 would very nearly buy you a new 10 inch dobsonian which would massively outperform both these scopes on all objects visually. Worth bearing in mind.

I think that is an often overlooked part of observing Stu.

Great piece Stu - thanks for that I'm motivated to spend more time with my Tak 100 and Lunt HW over the coming weeks and months now.

Oops !!!! I've just realised that I had the above images orientated to show the refractor / mak-cessegrain / schmidt-cassegrain view (using a diagonal). Here is the newtonian view:

The Pup star is further away from Sirius A than you expect. The gap is around 10 arc seconds so around the same as Rigel and it's companion star but the position angle is different and the brightness difference massively different. Its not like observing any other binary pair to be honest. Even with my 12 inch scope I've not had an observation where the Pup star was clear for prolonged periods. It pops in and out of view but consistently and in the same place. I've often tried to find an image or sketch of the pair that resemble the view through the eyepiece and it's quite hard. I came across this ultra-high magnification image recently that was acquired on 20 Jan this year so the position angle is current. I've oriented the view to match the Newtonian and I've enlarged the central portion of my sketch done in Feb 2019 for comparison. As you can see, typically, even with the best seeing and optical systems, the glare from Sirius A extends at least 5-8 arc seconds around the star so Sirius B is seen peeking though this. I expect people are actually seeing the Pup star from time to time but not quite recognising it for what it is 20-01-2020 image (not mine): My sketch:

It is a lovely target Seeing and transparency rather poor here tonight. Only the brighter stars showing and the seeing is not supporting high powers with my Tak FC100DL. Even Porrima is hard work ! I'm waiting for the moon to put in an appearance but I'm not expecting a great show under these conditions. Glad it's better where you are Stu.

Its rather faint and getting fainter now I think. Fainter than M81 and M82 (harder to see than those at least) and somewhat smaller. You scope should show it but it wont be obvious and higher magnification will help to tease it out of the background sky. I found around 80x helped when I last observed it with my 12 inch dob. A small, indistinct misty patch with a slightly condensed centre. Its breaking up apparently but I guess it could still do something unexpected ? https://skyandtelescope.org/astronomy-news/comet-atlas-will-it-become-a-naked-eye-object/

Perhaps a quick re-work of this fine piece Tim ?