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The beast is out!

Stu

By Stu
in The Astro Lounge

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Stu

Stu

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Believe it or not, I’ve owned this scope for about 18 months and NEVER used it! It’s been in the garage, tucked away behind other things but after a bit of a tidy up it was easier to get out.

So, with a decent forecast I thought I would get it out and give it a go. I think I’ll mainly concentrate on Orion, hopefully I can finally get a view of the Flame Nebula, something I’ve never seen visually (only via NV) so that would be cool. I think there is too much light pollution to go for the Horsey.

The beast, by the way, is a 16” home built (not by me!) truss dob in the style of an Obsession. I’m not expecting to be amazing at higher powers but hopefully it will serve a purpose as a nice big light bucket. Collimation of the secondary is tricky due to the three vane support design, and the secondary is huge! Much bigger than it needs to be so I will try to sort that at some point. It’s f4.2 if I recall correctly, and I do have a Paracorr to keep the coma at bay.

Lets hope it stays clear 🤞🤞

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Stu

Stu

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1 hour ago, Captain Scarlet said:

Very nice, I hope you have luck with the Flame. I see also you've lined up a spot of Badminton to help keep warm if it gets too cold :) ?

Magnus

🤣🤣 well spotted. No idea where it came from, we don’t play so it probably came over the wall from next door!

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Stu

Stu

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1 hour ago, niallk said:

The Flame is often disappointing from my location, but one special night - wow, loads of lovely detail!!  Those really transparent dark nights are like gold dust, but when they come along... 🙂

Yes, not sure how well I’m going to do tonight as the transparency is not as good as last night. We will see.

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Paul M

Paul M

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Hope it stays clear for you Stu, looking forward to the report from the beast. 

It's been a spectacular clear and deep blue sky day here all day, from dawn to dusk. Been on a 12 hour day shift and was looking forward to getting the new RC10 out under such a sky. Unfortunately before I got organised the sky deteriorated drastically. Looks like it'll be foggy soon.

No beasts in garden tonight :(  

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Stu

Stu

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Well, it was a good session, though not epic! I still class myself as a learner driver as far as big dobs are concerned; finding things is definitely a lot harder than with a refractor; harder work manoeuvring the scope plus a much smaller field of view and of course everything is upside down! Given that it was the first time I had used it, I expected some teething troubles and so it proved to be.

The TelRad works really well, positioned high up above the UTA, but I really need a RACI finder as well. Fitting one is a bit of a challenge as the UTA is only a single ring, but I’m sure something will be possible.

The motion is quite sticky, so I’ll have to have a look at that. When I tried it out in the daytime it seemed good, stays where you put it, but fine movements are more difficult.

Collimation of the secondary is difficult so I will have to look to modify how this works when I change the secondary to a smaller one. Primary collimation seems fine, although I think improvements can be made to the cell and how the mirror is held/supported around the edge.

I think the balance is slightly out, needing a bit more weight at the back. One of the good features of the scope are that the mirror box is fairly light, and easy to carry, then you add a series of weights under the mirror to reach balance. With lighter eyepieces I think it would be fine, but I was using a Paracor and 31mm Nagler so it was slightly too heavy. Easy enough to sort though.

Eyepiece position is fairly convenient, I just had to go on tip toes to see when at the zenith but don’t tend to observe there because of the dob hole challenges of manoeuvring the scope.

Overall though I’m pretty pleased, I paid a relatively low amount for a very portable 16” scope which I’m sure I can improve over time. I may even consider sticking a Nichol mirror set in it if funds allow in future.

So, what did I see? Nothing terribly exotic I’m afraid, and it was challenging getting properly dark adapted because I was in and out of the house sorting things out and lights kept popping on in the Kitchen just next to where I was observing!

I started by having a look at Jupiter and Mars. Let’s be clear, I have no expectations of this being a super planetary scope, but after a quick tweak of the collimation Jupiter wasn’t too bad. Plenty more colour than I see with small refractors and quite a few bands visible, plus a shadow transit but it wasn’t as sharp as a frac and whether it was seeing or cooling there was plenty of blurring of image. Mars wasn’t great through it so I didn’t persevere. I suspect that big secondary affects the contrast more than necessary.

I then spent a good amount of time on M42/M43 soaking in the views both with and without a UHC filter. I used the 31mm and 22mm Naglers giving x62 and x87 respectively and 6.4mm and 4.5mm exit pupils. Mainly the 22mm Nagler was used, but the wider framing of the 31mm was beneficial at times.

Without the filter it showed a clear green tint to the nebula, very distinct, and the extent and detail of the nebulously was wonderful. With UHC, even greener of course, stars still nice and an almost photographic view (just in moon green), batwings and fish mouth so clear, with a little Trap in the centre. Contrast was improved with the UHC obviously, really lovely and I popped up to the Running Man and could see nebulosity there, but no little man 😕. Probably my best views of M42 except when I had my C925 under darker skies with better dark adaptation at PSP some years back.

I haven’t often viewed M1, so gave that a go. Easy enough to find with the TelRad, and very clear with UHC (probably should have tried the OIII) Not much detail to be had but still probably one of my best views.

Other targets were M81/82, M97 the Owl Nebula and M108, plus the Starfish cluster. The lovely thing about the 16” is the image scale achievable whilst keeping decent brightness of the object, really nice.

No sign at all of the Flame Nebula, despite trying several time. I am sure my lack of dark adaptation was what prevented this but also I felt the transparency wasn’t quite what it was the night before.

If I get it somewhere properly dark then I think the views will be pretty amazing.

So, a decent start with the scope, plenty to do to improve it over the years which adds some interest, plus it is more manageable than expected so I must start using it more regularly.

 

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To aid in finding things I would make a leveling board, an adjustable setting circle and angle guage.  Finding stuff that way is a breeze.  Hope you can figure out the collimation issues as 16 inches worth of mirror is where the magic starts to happen 

Edited by Mike Q
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