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  #41  
Old 20-11-2007, 05:15 PM
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peterbat (Peter)
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Another possibility with regards to poor image quality might be to do with heat. If you are bringing your telescope outside from a warm house into a cold back yard it will take an hour or more for the mirror to cool down and give you the best views possible. I find it best to get the telescope outside, collimate while it is still light, then go and have tea and come back in an hour or so...

Dew is another possibility. While observing, use a torch to see if the secondary mirror is fogging up. Also have a look at your eyepiece, as a hot face can cause the eyepiece to fog up very quickly. A quick solution to this is to give the secondary and the eyepiece a short blast with a hairdryer.

Have you tried using the telescope during the day to focus on a distant object? A tree or a light pole on the horizon is a good starting point. This can also be used to help adjust the sighting scope / viewfinder so that what you see in the telescope eyepiece is centred on what you see through the viewfinder. Your telescope instructions should include something on how to adjust the viewfinder. Start with your lowest power eyepiece and work your way up to your highest power, refining the alignment of your viewfinder as you go. You will notice that as the magnification increases the brightness decreases, and any atmospheric turbulence becomes more pronounced, but this sort of testing will at least confirm that you are able to get good views through the telescope, and that what you are seeing through the viewfinder is what you are seeing through the eyepeice.

I'm sure the warning is not necessary, but I'll include it anyway... DO NOT USE THE SUN AS YOUR DISTANT OBJECT, OR TRY THIS IF THE DISTANT OBJECT IS ANYWHERE NEAR THE SUN OR MIGHT REFLECT AN IMAGE OF THE SUN INTO YOUR EYEPIECE.


Just my 2c worth, hope it helps...

Peter
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  #42  
Old 20-11-2007, 06:05 PM
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Tannehill
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Gso 12

I have a Bintel 12" and it works fine optically, albeit I use it in darker sky than you describe. So there is still no convincing explanation for your apparent inferior views, altho the mismatch of expectation and reality remains possible, as mentioned.

Other options:

Your optics (primary and/or secondary) could be severely pinched by the mirror cell and/or secondary holder, respectively. In the past this was a pervasive problem with the economy optics from China, but I believe it was largely remedied. Still, worth a check, if you feel comfy removing things. The primary mirror clips - with a rubber pad cushion - should be loose enough to slide a piece of paper between the under surface of the rubber pad and the mirror. The secondary clips should be similarly loose, but tight enough to prevent any movement of the mirror as the scope moves up and down. And give the secondary holder and spider (separately) a little wiggle, to see if there is any loose element like an overly-floppy secondary bolt spring or stripped thread on a collimation bolt.

Your mirror could be a lemon - a terribly poorly figured mirror, which slipped thru GSO's quality assurance system. Daytime assessment of collimation would not detect this. Really, only a star test would, and you would need a clear night to pursue this.

The collimation issue sounds like it's less likely the culprit now...however, the GSO does have floppy primary springs, as discussed, and the secondary spring also is no winner, leading to potentially clunky collimation. But one assumes the Bintel check of collimation would pick that up. And that is easily confirmed by an in-field collimation check. I suspect that collimation isn't your main issue, from what you've described and shared re your focuser tube views as you have provided.

Can you make a trip - without your 12 - to a club site to look thru others' 12 and comparable scopes, to assess the expectations/reality issue?

S
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  #43  
Old 20-11-2007, 07:22 PM
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GrahamL
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welcome terran .. sorry to hear of your first experiances in this great
interest being less than you hoped for .

the moons position in the night sky just after dark is a real killer to seeing much at this time every month .. like there it is right above us ..
throw in some local light pollution ..hey its summer and lots of folks are
outdoors or are planning to get back out under those flood lights they left
on .. dew.. mirror temps..you know there can be not a lot to see .

If you can get some stars to come to focus In a low power
eyepiece ( 26mm or so ) ?.. seeing is more likely your culprit.

A bit of high cloud drifting in ..the moon .. freakin inversion layers if your close to sea .. endless rain and clouds all conspire against us
"regularly" sometimes.. the good news is that the night sky moves slowly
what isn't to be seen this month will probably still be visible next ...failing that next year

If your scope has a major problem it will be sorted to .. despite your frustration for the moment hang in there .. you arn't missing much this week .. and some of the many good people in this comunity will likely be able to help out IMO .

take care
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  #44  
Old 20-11-2007, 09:57 PM
Terran
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There's only one thing I can do. Pack it up for now and wait for a time in the future when my brother can help me drive it down somewhere that others can check it out at night (maybe an observatory?). I've gone through everything repeatedly and it all seems fine, the telescope just has no ability to gather light whatsoever. It's as if there is no parabola on the primary mirror and it acts like a cheap $2 one. I can get into the darkest place I can find, and have spent many hours most nights trying since the last new moon, but all I see is nothing but stars, not even the slightest hint of anything. Just a faint view of the Orion nebula. As for the finderscope, I check that regularly and it only takes a few seconds to line up if I bump it. If it's too dark and I cant find a suitable target, I just use a structure of the moon as a quick aiming point. It's too simple and easy to mess up .

Quote:
Your mirror could be a lemon - a terribly poorly figured mirror, which slipped thru GSO's quality assurance system.
That is the only reasonable solution I can come up with . Explains it all perfectly. It reflects fine, it doesn't gather light any more than my bathroom mirror would.
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  #45  
Old 21-11-2007, 09:24 AM
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Terran

Have to agree with Mark's last post on the subject. I too thought that someone purchasing a 300mm telescope would have had quite a bit of experience with smaller telescopes and general observing of the night sky.

From your later posts, in my humble opinion, you lack the experience and your expectations are to great. Sorry about being outspoken.

YES, you may have a Lemon, but unless you have the experience to know what to look for and to test the optical mirror itself or have it tested by a experienced person you want know.

Why don't you contact someone in the science department in your local highschool? Usual there are always some students interested in astronomy and they might be only to willing to have a look at your telescope and give you some help or advice.
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  #46  
Old 21-11-2007, 10:18 AM
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chunkylad (David)
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Quote:
Originally Posted by Tannehill View Post
I have a Bintel 12" and it works fine optically, albeit I use it in darker sky than you describe. So there is still no convincing explanation for your apparent inferior views, altho the mismatch of expectation and reality remains possible, as mentioned.

Can you make a trip - without your 12 - to a club site to look thru others' 12 and comparable scopes, to assess the expectations/reality issue?

S
Hi Terran

IMHO, before you go chasing your tail looking for serious and time consuming solutions to this problem, I have to agree with Tannehill: ie try to get to an observing night and have a look through some other large Newtonians to compare apples with apples. in doing so, you can match your expectations with reality; and get some tips on issues such as collimation and suitable eyepieces for your Dob.

If you can manage to drag along your telescope, that would be ideal, but not absolutely necessary.

You'll find the folk at such a gathering more than helpful and willing to assist you.

Cheers
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  #47  
Old 21-11-2007, 01:01 PM
Hagar (Doug)
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Hi Terran, I had a 12" Bintel Dob and found colmination to be a real problem. One little bump and it was out. Replacing the primary mirror springs with a set of Bobs Knobs springs and knobs really improved the situation immencely. Be aware that reflected light from street lights or outside lights will grossly effect the view you get when looking through a large instrument without any knife edge baffles in the tube.
Don't expect miracles from any telescope, you won't see colour and you won't see the type of images posted on this web site with any telescope without using long exposure photography.
I can only say the guys at bintel in Melbourne have gone out of their way to help me over the years and I would think they will definitely try to assist you if they can.
Another alternative is to find a local astronomy group or similarly minded person in your area and ask for some assistance. You will generally find the astronomy community a fairly friendly and helpful group.

Good luck
Doug
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  #48  
Old 21-11-2007, 01:27 PM
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goober (Doug)
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I agree with Hagar - the springs on the Bintel 12" are very poor - I found it losing collimation just moving it in altitude. When I replaced them with stiffer springs, I couldn't believe how flimsy the standard springs were.

There are lots of variables with fast newtonians - work patiently through the problem, ask lots of questions. The best thing would be to get an experienced local amateur to have a look at your scope for you.
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  #49  
Old 21-11-2007, 01:30 PM
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iceman (Mike)
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Terran - even if you can't come bring your scope to our observing meet on the 8th December up at Mangrove Mountain, you should definitely bring yourself along.

You'll get the chance to look through some different scopes, and some nearly the same as yours. You can then test your expectations and experiences against a known quantity/quality.

I was on the edge of Long Jetty the other night trying to see Comet Holmes, and the light pollution around there was terrible with low hazy clouds.
If you still get stuck, i'd be happy to come around one night/weekend and have a look at your scope. But if you can, you should come up to the Pony Club on the 8th.
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  #50  
Old 21-11-2007, 07:21 PM
Terran
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I decided to call up Bintel this morning and tell them that the missing light problem is still there, and they ended up offering to get a delivery truck to come pick it up today for them to see it for themselves at night . Noone has come to pick it up today, so hopefully Bintel will be seeing through the scope thursday or friday night, and it will all be sorted out soon. To clear some things up regarding my lack of knowledge and experience, I will explain it with 2 short stories...

Rob - Buys a flashy car on a whim, hops in and starts it up. With no previous knowledge of cars, and using advertisements as an unrealistic reference of the car, he is very unimpressed with it. It doesnt fly over mountains, the speed stripes dont glow, and it doesn't go from 0-100 in 1/4 of a second. He is convinced it is broken because it doesn't live up to his unrealistic expectations. Rob also believes the world is flat .

Bob - Does his research before buying a car, hops in and starts it up. It doesnt start, the starter doesnt even try. He goes through the possibilities carefully, discusses it with others, and ends up descovering that his original idea fixed it. Once it starts, it has no power, wont even budge an inch. After going through all the possibilities he can think of, and in as much detail as he can without voiding the warranty, he is convinced the problem is a missing part in the gearbox. Bob is sure his expectations of forward motion are well within acceptable limits.

Bob would describe my situation. Notice the difference. I don't know the extent of what kind of views I can expect, but I'm not clueless and I do expect any astronomical telescope to collect and distribute a little more light than my naked eye at the very least. Besides a faint view of only the brightest part of the Orion nebula (which I can see with my naked eye), I see nothing but stars. That is as far as it goes. Other structures in the Orion molecular cloud complex that should be viewable, do not appear in the slightest at any time of night. Nor has anything else through many many hours of scanning the sky. This telescope does not show any more light than my naked eye. The images I see are clear enough, there is just no extra light there. To have a finderscope out of position and be convinced that the telescope isn't working is very foolish. Even bintel thought that was the case at first, and although I can understand how such things need to be ruled out, I assure you guys I wouldn't do such a silly thing. Having a finderscope out of alignment is very obvious and takes only a few seconds to fix with ease .

Thank you very much for the help offers and advice, especially those in PM and iceman's offer to visit me. There are some very helpful people here . But now that Bintel will be checking this for themselves, it's out of my hands for the time being. I will breathe a big sigh of relief if they confirm the same problem .

Getting to the pony club is almost impossible at the moment. But if that changes, I'll be sure to send a PM right away .
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  #51  
Old 23-11-2007, 06:21 PM
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Talking Hang in there mate.

Hi Terran,

I've been reading your tail of woe with interest, as I have just recently upgraded to a decent sized scope (GSO 8" dob). All I can suggest is to hang in there and hopefully all your problems will be sorted out shortly. When I first got the dob, I was away from home and set up in a caravan park just under one of the "street lights" in the park. As the other guys have said, light pollution will not be very good for seeing the dso's. I didn't manage to see many dso's with any structure or anything, but some brighter objects such as jupiter. When we got back home to a darker site, we started to see some dso's and planets with great detail. M42, 47 tuc, jup with cloud bands, saturn & its rings, etc, I'm still learning the night sky .
One thing is for sure; all the guys on this site will do their best to help you out, as I found when I asked for their advice before purchasing a scope. I just recently read Duncan's review of the 12" Gso dob, and he was blown away with it, you can find it here:
http://www.iceinspace.com.au/index.p...41,410,0,0,1,0

Hopefully you can get to the stage where you are confident in the equipment you have, and if you can get to a nice dark sky site, you too will be blown away with what you see.
Look forward to you sorting it out.
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  #52  
Old 23-11-2007, 08:28 PM
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Hi Terran!
If you're living at the Entrance, why don't you PM Iceman and/or others living in your area, arrange to have them help you, if you ask nicely!?!

I'm sure it'll be better to help by seeing the telescope than doing it over the web....


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  #53  
Old 24-11-2007, 06:56 AM
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Hi Terran
Sorry to hear (read) of the difficulties with the new scope. I hope you get it sorted! In the expectation/reality debate I've found the astronomical sketches give a fairly good impression of what you can expect to see - f'rinstance this link http://www.skyrover.net/ds/ds_detail.php?id=183 (with invert button pressed) shows the Orion nebula pretty much as I see it from a light-polluted back yard through a 200mm dob.
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  #54  
Old 24-11-2007, 09:49 AM
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Please update us once you've got it all sorted out...

s
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  #55  
Old 17-12-2007, 10:23 AM
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Hi Terran,

Did you end up getting your scope sorted out?
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  #56  
Old 17-12-2007, 12:18 PM
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In the absence of any feedback from Terran for a number of weeks , and after a lot of attention and concern payed by IIS members to his plight , I can report ( 2nd hand) , that an experienced amateur astronomer had a few enjoyable nights road-testing his 'scope from home and found all to be completely normal. Full credit there for thorough Bintel after-sales service

Looks like a classic case of trying to learn to walk before you can crawl... Beginners take note ..

Last edited by Satchmo; 18-12-2007 at 10:07 AM.
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  #57  
Old 17-12-2007, 02:11 PM
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I was reading this thread and thinking that. A Dob ain't the most complicated of instruments.
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  #58  
Old 17-12-2007, 02:15 PM
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Ditto, on all accounts, Mark
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  #59  
Old 17-12-2007, 09:02 PM
Terran
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Hi Guys,

The reasons why I didn't respond was that I only just got the telescope back recently (after some delays over misunderstanding the problem), and because of the recent changes to the IIS terms of service. The shop told me that they lent it to an amateur atronomer to test and that he/she was able to take pictures with it. The shop told me there was nothing wrong with it and that I must be using it wrong. But seriously... how could anyone not use it properly when it's so simple? After I got it back, I expected things to be the same, but noticed a clear difference in the light and visibility. I am getting enough light now that I get glare and streaks from the brightest stars, and I'm able to clearly see a couple of star clusters now. Nothing else though as of yet besides some circular glow around brighter stars which I'm yet to identify as objects or a lighting effect (I've only spent an hour with it since I got it back). I'm still waiting on my laser collimator, which was supposed to be in stock as of 2 weeks ago. Hopefully I'll have it back soon.

I still suspect that light pollution might be affecting things to some degree, but with no real information available regarding light pollution levels and their effects, I will have to test the telescope in a far away dark environment some time in the future.

But for now, I've already given up going in circles over this and have no intention of wasting more time on it. Thank you for your time and concern.

If the IIS management feels the need to remove this thread, that's ok with me.
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  #60  
Old 17-12-2007, 10:12 PM
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Hi Terran,
I'm sorry that you feel that the scope still isn't right.
I think the best advice that you should take up immediately (and there has been a lot of it from the members) is to take your scope to an observing night with the Central Coast IIS mob, and compare it directly against other 12" Newtonians.
I know Mike has offered his service.
A direct comparison will immediately answer your concerns, as most of the scopes owned in that size are G.S.O sourced.
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