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Newbie question... is my telescope "non-standard"?


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Hi everyone.

 

I've just bought a cheap reflecting 'scope from eBay. 80mm × 700mm so I should see something. Ok?

 

I think I need to collimate it as it doesn't focus with its high mag eyepiece, but I just discovered that the internal diameter of the focus tube and eyepieces are 1".

 

All the collimators and eyepieces I've seen on the internet say they're either 1.25" or 2"

 

So, am I stuck or have I misunderstood something?

 

Thanks

 

Laurie

Edited by Laurieo
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What is the focal length of the 'high mag' eyepiece? Does it actually fit into the focuser draw tube? Newtonian scopes are notorious for focusing issues. You may not have enough back-focus. It might be that you just need an extension tube.

 

SbZzE6b.jpg

 

Half of the eyepieces I own won't achieve focus in my 150mm GSO Newtonian. Some won't even with an extension tube.

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The eyepiece says "SR6mm". I don't know what SR means.

 

It does fit in the focus tube, and I can focus 'before' and 'after' but in the focus spot the image in blurred.

 

I should have said, this was whilst trying to view Jupiter. Since having the scope the moon hasn't been viewable, so I haven't tried it with a nearer object. 

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13 minutes ago, Laurieo said:

The eyepiece says "SR6mm". I don't know what SR means.

 

It does fit in the focus tube, and I can focus 'before' and 'after' but in the focus spot the image in blurred.

 

I should have said, this was whilst trying to view Jupiter. Since having the scope the moon hasn't been viewable, so I haven't tried it with a nearer object. 

 

It may be an inexpensive Ramsden type of eyepiece. It would give you about 117x in your scope, I think. It may be just a poor quality eyepiece. It doesn't necessarily mean the scope is at fault. Jupiter is notoriously difficult to get a sharp focus on. It's very bright at the moment, which isn't helping particularly. The seeing may be a factor. Especially if Jupiter is low as you are looking through a lot of atmosphere. Thermal distortion emanating from houses etc also.

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It might be worth buying a couple of reasonably priced Plossls. These are perfectly good eyepieces that probably won't break the bank. With my 80mm, 72mm and 60mm telescopes I often can't get a sharp image above 90x on Jupiter. A few weeks ago I had a sharp 200x with a 127mm Maksutov Cassegrain. Conditions and the jet stream are always a factor in observation. The jet stream often misses the entire country. Sometimes it covers it. When it misses the country the seeing is generally better.

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Ahh, that's interesting, thanks. I don't think it's to do with the seeing as there was no sense of waviness or shifting, the image I could see was quite static and solid. Having said that, the image of Jupiter though my lower powered eyepiece was mainly white with a blueish band around the edge.

 

Maybe, before loosing heart I should wait until the moon is up and see how that looks

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A lot of people are finding Jupiter a bit 'washed out of colour' at the moment. It has been closer to us than it has been for years. Have you tried Saturn yet? A bit easier than Jupiter and you can see the rings at magnifications of around 40x (or less). Titan can also be pretty easily seen with a small scope.

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3 minutes ago, Laurieo said:

 

Thanks, yes I may get some, but it does go back to my original question... the Plossis are 1.25" and my focus tube (and eyepieces) are 1".

 

 

 

Oh right, sorry I forgot you have a .96" focuser. You may be able to get an adapter, but there will probably be some vignetting.

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  • 2 weeks later...
On 10/29/2022 at 1:22 PM, Laurieo said:

Thanks for the reply.

 

It's a Jessops compact 80mm × 700mm.

 

1667042254745390372834146978206.jpg

As far as I can tell from googling, that scope has a spherical mirror (not parabolic). If you remove the eyepiece etc from the focus tube (the small tube on the side) you should be able to tell if there is a permanently mounted lens at the bottom of it - try moving a pencil or a finger on the inside of the tube (careful not to mar the secondary mirror) and look through the (empty) focuser tube. If you see the pencil/finger and it looks like you're seeing it through a lens, that means the telescope is a Bird-Jones design.

If so, you should curb you expectations as you won't be able to use a laser collimator, for instance. More information on the Bird-Jones design in the link below.

Don't hate me for saying this, but if the scope is a Bird-Jones design you will probably find that a good pair of binoculars supported by some sort of stand/tripod works better even though you get much lower magnification.

 

https://telescopeboss.com/what-is-a-bird-jones-telescope-and-why-do-people-hate-them/

 

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On 10/29/2022 at 12:17 PM, Laurieo said:

I think I need to collimate it as it doesn't focus with its high mag eyepiece

I recently went for a very cheap used Sky Watcher 114mm/1000mm reflector myself, and was disappointed that I didn't seem to be able to get sharp focus even when using a 20mm eyepiece, after having collimated it as best I could using the video below.

Discovered that it had a spherical mirror and Bird-Jones design, as mentioned in the last post. As I was spoiled by having a 120mm achromat telescope from before I gave up on it - I might make a xmas present of it to my nephews though. You can still use it, but focusing on the planets will be tough.

 

 

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I don't think I would put much effort into this scope.
Most 0.965" eyepieces are poor quality. OK there are exceptions.
It looks like it is a 'Bird Jones' that I have yet to hear a good word about.
Most packages like this get used a few times then sold on.
Get what you can out of it without spending and think about a different scope.

 

To try things, you don't need a night sky. My favourite checking targets are a brick chimney and an electricity pylon at 2KM. I use these in daylight to check for scope problems.

 

The bluish band you report is probably chromatic aberration in the cheap eyepiece.

 

Looking at the mount, it is more suited to wide field views, not astronomy.
Remember the moon is about 0.5degrees wide. Jupiter about 1/60th of this size.
You need a very stable mount and tripod.

 

If asked, most in the hobby will tell you to avoid ebay, gumtree, the car boot sale, online general sellers (Amazon) and department stores. In fact the only retailers for new scopes should be specialist astronomy retailers.
These people want you to come back for accessories and more scopes in the coming years.
Importantly, they are able to advise when you have problems.

 

I'm sorry if this sounds blunt and negative. But I think it unfair to string you along in expectation of brilliant views after a few tweaks.

 

By all means try a few things. Scopes are something to learn from. Not just plant on the ground.
The lessons learnt from this scope will teach you what to look for next time.
Hopefully this will set you along the path of....... my next scope needs........

 

HTH, David.

 

 

 

Edited by Carbon Brush
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Thanks for all your comments.

 

I do appreciate that you get what you pay for so I'm not expecting much from this 'scope, but as I may have said, at this point of my life (I'm a pensioner) I can't really justify spending a lot on a "toy" so I've gone for the option that a cheap telescope is better than no telescope.

 

You never know, I may win the lottery or an unknown rich relative may die leaving me a fortune at which point I can get something decent, but in the meantime I'll do the best I can with what's available.

 

Cheers

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TBH an ST80 is a very capable scope. You will be surprised how much you can see with one of these.

 

G0KQtrWl.jpg

 

Although it does depend on how much you can afford. 

 

bUxsxRGl.jpg

 

If you think you can go at least 200 quid the Sky-Watcher Explorer would be more than adequate. It might be best to sell the Bird-Jones and save for something a little more capable. You wouldn't be disappointed with an ST80 or Explorer 130.

 

 

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A vote for both scopes suggested by Nightspore.
I have an ST80 and they give a lot for the ££ spent.

 

Keep an eye open (no pun intended) for anything on sale not too far from you.
Is there a local astronomy society you could vist?
A chance to look at and through scopes. Maybe someone will have something for sale?
Maybe someone local can help you check over anything 2nd hand locally?
 

As a general rule, you are better off buying 2nd hand scopes within the astro community.
They tend to be well looked after and you get honest reports of what to expect.

 

Keep visiting this site. There is lots of good advice to be had.

 

David.

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