Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Altair Astro 8" f4 Imaging Newtonian


earth titan

Recommended Posts

No worries folks. All valid points.... :D

I wish I could afford to buy a premium set up for imaging but as a self employed consultant to the manufacturing sector :icon_scratch: cash is, as you can imagine, tight.

I love the thought of a 100mm apo, a carbon tubed astrograph or even a steel tubed f4 quattro on an EQ6 but the cheapest of these OTAs is £500 with a coma corrector - where as mine was WAY less then that.

I enjoy tinkering and really get a buzz out of making the most of what I have, so perhaps this could be the last post on the wisdom of buying this scope and revert back to an account of the modifications made by those of us that have them and results we are getting.

I'm sticking with mine until I outgrow it - which will be a while yet.:(

Link to comment
Share on other sites

  • Replies 105
  • Created
  • Last Reply

My (ex-physicist) "spider senses" tell me that, without significant improvement in e.g. basic collimation adjustment design, the "theoretical" demands of F4 Newts are not (easily? ever?) going to be matched by £400-500 technology. That as a given, I see no harm in TRYING... :D

I can definitely relate to MINIMAL budget types. LOL. However, these threads provoke discussion (experimentation!) that I actually learn from. Of course, I'm only using MINE to cover a 1/2" (6x4mm really!) Watec video-cam chip. :(

I'm never going to set the (SGL) imaging world alight. On most topics these days, I'm usually either ignored or "lectured to" (being frank). But, expectations aside, a modicum of enthusiasm for this topic? I can actually relate to some of this stuff... :icon_scratch:

Link to comment
Share on other sites

I know you guy's are getting on with it but jeez.... are these not 'imaging' scopes? why all the trouble, surely the supplier should be able to do this on your behalf, I'm reading this with total amazement that it didn't arrive ready for a quick collimate and then imaging session..

99% would have returned them.. I for one am not buying one because I cant be bothered with the head ache.. It'll be a quattro for me , hope it comes with tube rings tho or I'll be eating my words.. :icon_scratch:

You quite right Guy you shouldn't have to jump through hoops like this as it shows it not up to the job off the shelf. I sent my first two back and then decided to sell the third as I preferred using my refractor

Link to comment
Share on other sites

My (ex-physicist) "spider senses" tell me that, without significant improvement in e.g. basic collimation adjustment design, the "theoretical" demands of F4 Newts are not (easily? ever?) going to be matched by £400-500 technology.

This is an interesting thread. Macavity makes a good point. Over the last year or two we have seen a number of budget 'imaging' reflectors and refractors that fall short in one area or another.

I don't often comment in threads that discuss a product that competes with one of ours but I have been asked a number of times for an opinion so here goes: I expect the GSO 8" f4 (in whatever guise) is optically on a par with a Skywatcher Quattro, but not Mechanically. In particular the GSO mirror cell is not as precise or as robust. To be fair the GSO is often available at a lower price and so-long as the owner is aware of the shortcomings and is happy to make a few modifications it can offer similar results. And if the modifications don't work you can upgrade the entire mirror cell.

That is about as objective as I can be :icon_scratch:

HTH,

Steve

Link to comment
Share on other sites

This is an interesting thread. Macavity makes a good point. Over the last year or two we have seen a number of 'imaging' refractors and reflectors that fall short in one area or another.

I don't often comment in threads that discuss a product that competes with one of ours but I have been asked a number of times for an opinion so here goes: I expect the GSO 8" f4 (in whatever guise) is optically on a par with a Skywatcher Quattro, but not Mechanically. In particular the GSO mirror cell is not as precise or as robust. To be fair the GSO is often available at a lower price and so-long as the owner is aware of the shortcomings and is happy to make a few modifications it can offer similar results. And if the usual modifications don't work you can upgrade the entire mirror cell.

That is about as objective as I can be :icon_scratch:

HTH,

Steve

Steve- Thanks for the above, I totally agree with what you say. I suppose at the end of the day it comes down to the old saying of 'you gets whats you pays for!'

I have Kevin's Altair Newt and after removing my overload of silicone and re-doing it again with only 3 'blobs' a quite session on M42 last night showed much improved stars and I'm very happy with my scope. If the Quattro's were the same price, then it would be no contest, Quattro every time but with a little tinkering the cheaper GSO looks to be just as good.

Link to comment
Share on other sites

All interesting reading and making me think as well.

I have double the trouble of getting the GSO working at F2.8 :):eek::D

I am still getting colimation issues, and more mods are needed.

I would definately say, these scope and especially mine with the reducer / corrector are not for the faint hearted. But I like to tinker and play, it is all part of the hobby and for £1800 I am going to persist a bit more with my carbon 8inch GSO.

BUT

Even in this state, I am getting result far exceeding my expectations. 5 min subs on bodes under moonlight showing clearing the Integrated Flux, wow !!!!!!

Craig, Blinky, Glad the silicon re-mod has helped a bit, you have to keep this mirror floating.

Link to comment
Share on other sites

Sorry, missed a few bits of the thread, was busy imaging :)

Tom, the first pic you posted looked light the secondary was slightly rotated, putting the stars on one side out of focus and stretched.

Looking down your tube, I think I would be inclined to flock or paint the front face of the first baffle maybe. It looks quite bright in the pic, maybe its not so bad? But if it does have the potential to reflect some light back towards the secondary, then it might be best flocked. (You've done a cracking job btw!)

I had some problems with star shapes last night, simply due to the rapid drop in temperature. To be fair to the mirror you need to give it plenty of time to cool properly, and when the temperature outside is dropping rapidly, that will take longer than normal. When the temperature bottoms out, the mirror will catch up some time after, and that is the time to be examining star shapes and star testing. The effect on my 10" mirror was dramatic last night, I was nearly tearing out what is left of my hair until I figured out what was happening!

While I was mucking about last night I made a hotspot for my GSO 8" F4 and then collimated it. I have a friend who is interested in astronomy so I might lend him the scope for a bit.

There was a comment earlier about the donut's and centring them. The Catseye method uses a transparent overlay with the mirror sizes marked on it, foolproof! If anybody wants to use my template and lives local enough (Coventry) to make it worthwhile, just shout. The mirror on my GSO is a shade under 8".

Vic Menard in his collimation book makes the point that pretty much every scope he has seen, the optical and physical centre are so closely correlated that best practice is to take the physical centre as the optical one.

The thing that stands out, is that F4, tiny adjustments have a BIG effect on the resulting image, and so the more accurate we can be at every possible adjustable stage, the better the final result. And even then, circumstances will conspire to bowl you a googly every now and again :D

Cheers

Tim

Link to comment
Share on other sites

Thanks for the encouragement folks. Current mirror securing looks good - will see how it holds. Think I'm headed in the right way - fingers crossed.

Been doing some work to imrove mount smoothness (have to question Chinese build quality sometimes - drive gears only meshing 50% and loads of backlash). Just trying to find some lithium grease.

Awaiting an adaptor to make my finder into a guidescope to keep weight down for guiding. Am to going to flock under the 1st baffle before the mirror goes in.

Am interested in the catseye system, but can't get a full understanding of how it works. Presume you need the ''stickers" and a collimating tool?

Link to comment
Share on other sites

Am interested in the catseye system, but can't get a full understanding of how it works.

That was me all over, and for that reason held off investing in it for a couple of years. I now know that was a mistake because the tools are an absolute pleasure to use, and much more accurate that a standard chesire.

I bought the triple pack, which consists of a calibrated and adjustable sight tube, a calibrated chesire that matches the hotspot sticker (a pure joy to work with, no guesswork), and the twin pupil autocollimator. With it comes everything you need including the mirror marking template. Everything about the kit is really high quality, even the little red LED clip on torch they supply, all in a rugged ABS case.

As a bare minimum, get the Blackcat Chesire, and the twin pupil autocollimator, and the hotspot. The whole kit is pricey, but worth it I think, especially with these fast newts where collimation is so critical. You are also able to see what, if anything is moving out of collimation, and so take steps to correct that.

Cheers

Link to comment
Share on other sites

Stick with it guys, I have had mine now for a while...yeh I agree you have to mess about with it at first...but.....and here is the but... when all is sorted you will be amazed at what this scope can do for the money! I nearly sold mine recently but have decided to keep it. There is a guy on here called luis campos, he has one of the these scopes. When I first got mine I got in touch with him, he pointed me in the right direction and since then I have never looked back. As I said for the money...this scope is a serious bit of kit!! Any questions then send me a mail, will be happy to help!

Link to comment
Share on other sites

  • 3 weeks later...

Making the most of the full moon, just an update.

  • Bobs Knobs up-rated springs ordered, arrived and fitted
  • Focuser checked for square (perfect)
  • Laser collimated
  • Mirror re-center dotted (this time with millimetric precision)
  • Primary now fully floating but 'shimmed' in place following the suggestion from Catatonia and clips 'loose'
  • Secondary realligned with the recollimated laser
  • Collimation checked with barlowed laser, cheshire and laser. All agree!

Just got to wait for an evenings session with clear skies and no full moon so I can test it. :D

Link to comment
Share on other sites

  • 3 months later...

You may remember the problems I had with this scope when I first got it. Most disheartening:mad:

However, after a few months of despair the penny dropped. The distance between the back focal plane of the camera and the coma corrector is actually important

:hello2:

So here we go. The image below is 1000% better.

:)

Still got some minor issue with polar alignment, but when the weather clears up I'll get these sorted.

post-19169-133877783515_thumb.jpg

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.