Captain Scarlet

On 19/10/2020 at 02:13, Sunshine said:

I once drove almost two hours to a dark sky site, only to realize as i was setting up that i left my eyepieces at home on the kitchen table.

I recall reading @Stu doing something similar...

2 minutes ago, John said:

Mine is an OO 300mm with a focal length of 1590mm so 

Ah yes mine will be 300 not 305 so 5.3 of course. Given both Orion, obviously the same mirror ☺️
 

I have had no problem with any of my other eyepieces but then I wouldn’t, seeing as the next up was my 18.2 so cutting out much of the coma’d area.

As you say perhaps you are just not sensitive to it. I hope I haven’t caused you to “once you look for it you can’t again miss it”.

35 minutes ago, Alan White said:

... Having just bought a Nexus DSC for my dobson, also of interest too,
is that running with a SW AZEQ6?

Yes I drive my AZ-EQ6 with it. It generally works very well, but the menu logic for it takes some learning, specifically the functions of some buttons. There's one particular sequence of button-presses during alignment that is intuitive obvious and logical, but WRONG and fatal (to the alignment). Once you make that mistake, you need to reset the scope position and start again. I do it almost every time. But once you've got through that, it's very good. You can use everything you observe as an extra alignment point, so it gets more and more accurate during the session. The "Tour" feature, the catalogue-selection, the sheer number of catalogues, and the notes on each object, are all brilliant.

I have ordered an encoder unit for my AYOii mount which is due soon, so I'll be able to use the Nexus DSC in "push-to" mode as well, as originally designed. And in due course I intend to get a largeish Dob.

33 minutes ago, John said:

Very interesting report - thanks for posting it

It is interesting to note the differences in coma between an F/4.9 newtonian and an F/5.3 (which I have). I guess there will be some present at F/5.3 but even with my 100 degree AFoV eyepieces I don't find that it is noticeable.

Good to know that the Paracorr will do the job if I do start to notice it

Funnily enough the OO mirror I ordered during Lockdown has just been completed and is about to be delivered. It is 1590mm apparently and is intended to replace my SW 1500mm, turning my f/4.9 into a f/5.2 - the comparison will be interesting. Though I'll need to do a bit of tube-surgery to install it. In time I'm going to order a custom carbon tube for it.

2 hours ago, Louis D said:

Did it require any additional in-focus relative to the eyepiece alone?  My GSO CC requires 11mm of in-focus.  As a result, neither my 25mm Paradigm (Starguider) or S-W 5-8mm zoom will come to focus with it (I have a very low profile focuser optimized for an undersized secondary).  I've read it is anywhere from 10mm to 19mm.

It did, I think. I thought initially it could simply replace the Baader 58mm extension on my Steeltrak focuser, but by doing that and sliding the Paracorr all the way in I couldn't reach focus. Luckily it has a very long nosepiece, so I just drew it out a bit and achieved it. Looking closely at one of my pictures, it does seem like about 10mm. I'll measure and compare properly in due course.

I think the suggestion of a disappointed child's letter to the Council or someone, suitably publicized perhaps as an Open Letter, is not a bad idea.

Also perhaps make sure to wear Hi-Viz vests when observing, they are incredibly distracting, even slightly annoying, to anyone just behind a bright light, so whenever you are all out there, the neighbours from the top windows will see these bizarre bright shapes and stripes moving around the otherwise inky darkness.

M

If you follow the thread What Did the Postman Bring? (esp @PeterW who requested a report), you may have noticed that I received a new Televue Paracorr Type 2 Coma Corrector yesterday, for use with my SW 300p f/4.9 newt. And what's more, the very day it arrived was forecast to be a perfectly clear night.

Amongst my eyepiece collection I have a Televue Panoptic 35mm, which in theory was for use as a widefield eyepiece but whenever I have used it, such as to show the Pleiades to my neighbours last weekend, I've been disappointed by the severe coma-stars starting not far from centre-field. I've even been considering selling the Pan 35 for that reason, and have rarely used it. So I was especially curious to see how much of a difference the Paracorr would make.

I set up last night as usual, without the Paracorr to begin with to have a direct front-of-mind point of reference, and after alignment I slewed straight to M45. Sure enough, the stars were spangly and the view was annoying.

I put in the Paracorr, rotated the slider to setting "G" as per instructions for the Pan 35, inserted the eyepiece itself, and with a sense of trepidation I took a look.

I no longer plan to sell the eyepiece.

The view was suddenly wonderful. A field of extremely bright, pinpoint stars all the way to the edge, just as M45 should be. Sure some diffraction spikes on the very bright ones but I don't mind those. I went on a tour of open clusters, M37 with its central red bright star, M36, and a host of fainter but no less more-ish clusters in the vicinity, using my Nexus DSC and its brilliant "Tour" function set to "within-10-degrees".

It's expensive but it has completely transformed wide-field viewing with my medium-sized newt.

Cheers, Magnus

... further thoughts. Either a suitably large rubber band which means you don't need to unscrew the tube completely. Or some PTFE tape around the threads, which means you probably will. Or both.

M

The blue tube, as I understand it, screws onto the rear plate. The black rubber/plastic ring both seals it and acts as a sort of "spring-washer" to lock the thread. If the rubber ring has broken, the thread is freer to wobble around. See my detailed post here about disassembling my own Skymax 180, whose design is similar but has the middle tube bolted to the rear cell rather than threaded on. Your scope I believe will have a similar overall design, apart from the threading of the tube. The main collimation bolts, for example, hold the whole primary mirror in place and are its only connection to that rear cell. DO NOT undo those collimation bolts!

I think you can safely unscrew the whole tube from the rear cell and lifit it off to expose the innards and primary, but be careful when balancing it on just the visual back! You'll need to find a replacement large O ring or similar way of preventing the thread wobble, maybe some thread-lock?

My verdict: totally fixable. I hope that's been helpful!

Cheers

Magnus

I’m seriously beginning to think my corrector is obviously rubbish. The very day I get it, there’s not a cloud to be seen and it’s due to stay that way all night...

19 minutes ago, Barry-W-Fenner said:

I will be really interested to hear your thoughts on the PC Captain.

I am toying with the idea of a coma corrector of some sort for my 300p.

It will be good to hear how sharp your stars are after installing this.

Baz

Mostly the unavoidable coma on my newt I've either not noticed or not minded. But that's likely because my lowest power 1.25" eyepiece was 18.2mm giving 82x, enough I guess to miss out most of the coma-affected parts of the image circle. But I've lately got a 24mm and started using my 2" 35mm eyepiece a bit more, for example on the Pleiades, and with those, especially the 35, the coma is really annoying. I'm really excited about this, I'll report back in due course...

M

This arrived, to go on my 300p:

“I damn well paid for them so I’m going to use them!” is their attitude. Such a shame. If you take that approach with extra fog lights on your boy-racer car the police stop you if it’s not actually foggy. A pity there’s no similar enforcement here.

M

I have an M2, not the “c”. It came with a rather tall pillar which is what I “grab” when I want to take it out. It’s very good once the tripod head is levelled and the fore-and-aft balance of the scope is set. You can set the friction knobs to very light and the thing is as smooth as you like., responding to fingertip touch.

One of my favourite asterisms. I've added the Oyster Nebula to my observing list...

M

3 hours ago, Louis D said:

You can ask a moderator to delete the extra posts.

I've had it happen when my internet connection was flaky, and I hit return multiple times before it actually posted thinking the first time didn't work.  They all got queued up until my connection returned.

Better on here than on Amazon I guess!

3 hours ago, Steve Clay said:

How you getting on with the M2 Magnus?

Regards Steve

I really like it. As with any such alt-az, it’s very sensitive to the tripod head being level. If it is level, and the scope balanced, on light friction settings it just needs the lightest touch to move it to a new position and it stays there.

Did you fit the guide handle or was that part of it?

Weds is looking good for me clouds-wise so thanks for this!

M

Yes I had intended to inflict the double-double on them too, but it was at almost exactly the same altitude as Albireo and the back end of my newt would've struck the tripod. I need the AZ-EQ6 extension pillar: I've been meaning to get one for ages now.

When I first saw them, the only (so far) objects that I myself have said, on my own, out loud, WOW! have been M13, M57 and the double-double.

Persuade her to lend you the money. You pay her back £300 pcm for 12 months. She makes a profit. You get your scope. Win-win.

☺️

M

Last Sunday my neighbours asked when was the best time to look at Mars? Which I interpreted as them having read about Mars' current close proximity, knowing I have telescope(s), and requesting a good look. Naturally I obliged, and suggested Tuesday evening, school night notwithstanding, as it was forecast clear. It was also due to be Moonless and clear, so I after finishing work I set up 2 scopes, my 12" on the big AZ-EQ6 and my little 6" Intes on the Stellarvue M2. I drew up a short list of other targets that might interest them aside from the Red Planet.

They turned up, and we quickly turned to Mars.

As I had expected, and although they didn't admit it, I suspect they were somewhat underwhelmed by the view. In my experience, it was a good view, seeing was quite good. Dark regions were easily on show, but I think they were expecting D Peach or Hubble. Oh well. This was exactly why I had other targets in mind.

I directed them, naked eye to begin with, to the Andromeda Galaxy, then we turned to binoculars. They were more impressed by that.

Next, and from their point of view this was the absolute star of the evening, was M13, the Great Hercules Cluster. They'd never heard of Globular Clusters, and I'd deliberately not told them what we were about to see. First, like M31, we just about were able to make it out naked eye, as a "something" brighter patch maybe not a star, 2/3rds the way between the two stars on the right of the keystone. Then we brought binoculars to bear, and they definitely saw it was not a star, but a circular graduated haze, more or less bracketed between a couple of brighter stars. Finally I let them look through the 12". They were absolutely blown away. It was so gratifying.

Uranus came next, an obvious bluish disc. They liked that, too.

Albireo, aka The Jewel of the Sky, was too high, I know from experience my 12" newt would've suffered "mount-strike", so I chose instead Almach which is better in two respects: its colours are deeper, and it's a true binary unlike Albireo. They loved the colours, and I never tire of Almach.

Finally I put in my Panoptic 35 giving me 43x and 1.6 FoV, and we headed to The Pleiades. We first of all tried to discern as many stars as we could naked eye. Then through the eyepiece, they loved the field of super-bright stars and inky background, such fine jewels.

So it was an unexpected neighbour-demanded observing session which I almost certainly would not have done without the prompting. It was interesting that Mars was the initial motivation but disappointed them, and that M13 was the real, er, star of the show: I always suspected it should be, as it's so unexpected. And we saw lots of meteors too, mostly funnily enough coming from the South West, not sure what xxx-ids they were.

Cheers, Magnus

9 minutes ago, DainiusU said:

Great post, thanks! I have a question here - are these two boots holding something or I can safely remove them and attach bracket using them later? I was afraid the hold focuser or something else and in doubt can I remove them both without the consequences?

 

You can safely remove them, they are for a finder bracket, allowing the finder to be “above” the dovetail whichever side of a mount you set the scope.

I also very recently got around to comparing what I was supposed to be seeing (sky safari pro) with  what I was actually looking at and was gratified to notice those moons too! Only a couple of weeks ago. So I can feel your joy!

M

11 minutes ago, Louis D said:

... Perhaps there are other areas in Europe with dark skies and stable seeing conditions?

Fair enough re all those other types of targets.

Regarding European really dark sites, there are not many easily accessible. I’ve based myself partly in extreme SW Ireland which is one of those places, and a big dob is on the wish list. I have a 12” but hanker for twice that.

M

The trouble with very large aperture scopes is that the minimum magnification for a standard exit pupil gets too high, unless you go ridiculously fast.

For example, 1000mm aperture f/3 with an exit pupil of 7mm implies minimum youthful magnification of 143x, and even higher if you’re older! That completely rules out extended nebulous objects which is what the large apertures are primarily aimed at.

M