30 replies to this topic

[gdeihl]

Back in April of 2021 I purchased a 10" Zhummel Dobsonian telescope. I got a lot of good advice concerning questions I asked, but I'm now struggling with whether or not to continue trying to make this telescope work for me. Everything in the eyepiece is out of focus. I've tried collimating, but it made no difference. I probably shouldn't have taken the scope apart and cleaned the primary mirror without checking this first (it was cloudy for weeks after I bought it and got impatient to do something with the scope). I tried contacting a local astronomy club but got no response. I still haven't gotten the issues with my base resolved (sticks turning side to side). I put the scope aside in late 2021 after being frustrated for way too long and haven't touched it since besides taking it upstairs to a spare bedroom and putting a cover on it.

 

Before I give up and sell this telescope does anyone live in the Buffalo, NY area that can take a look at what is going on with it and help get my problems resolved?

[vtornado]

Everything in the eyepiece is out of focus.

Did your telescope come with an extension tube?  This is a 1.25 or 2 inch diameter tube that goes into the focuser before the eyepiece. Many of the newer telescopes need this in order to come to focus with eyepieces.  It may be easier to test focusing in the day.  If you don't have an extension try not seating the eyepiece all the way in the draw tube.  To experiment, use the lowest power eyepiece. (longest focal length 25mm??)

 

Another trick is to use a small piece of waxed paper.  point the telescope at the bright sky (not the sun) and hold the waxed paper over the focuser tube without the eyepiece.   Move it closer and farther until you can see the image.  That is the focal plane.  The focuser would have to be raised to that same height with a seated eyepiece.

 

I still haven't gotten the issues with my base resolved (sticks turning side to side).

Does this base have teflon pads or a lazy susan bearing?  Watch the upper board (called the azimuth board)  carefully in the day when you rotate the scope.  Is it flat or warped?

Is there a tension adjustment bolt in the center of the azimuth board?   Have you loosened it?

 

I tried contacting a local astronomy club but got no response.   Try again, this is not a professional help desk with service now ticketing system running.  Your request may have just gotten lost, or the ball dropped.

Edited by vtornado, 06 February 2025 - 12:23 PM.

[Scope2]

Don't give up yet!  Probably just need to adjust the primary a little to reach focus. Local Astronomy clubs usually post when they have observation nights.

The Buffalo Astronomical Association may be near to you. phone 1 716-870-3115   best Regards, Pat.

[gdeihl]

Everything in the eyepiece is out of focus.

Did your telescope come with an extension tube?  This is a 1.25 or 2 inch diameter tube that goes into the focuser before the eyepiece. Many of the newer telescopes need this in order to come to focus with eyepieces.  It may be easier to test focusing in the day.  If you don't have an extension try not seating the eyepiece all the way in the draw tube.  To experiment, use the lowest power eyepiece. (longest focal length 25mm??)

 

Another trick is to use a small piece of waxed paper.  point the telescope at the bright sky (not the sun) and hold the waxed paper over the focuser tube without the eyepiece.   Move it closer and farther until you can see the image.  That is the focal plane.  The focuser would have to be raised to that same height with a seated eyepiece.

 

I still haven't gotten the issues with my base resolved (sticks turning side to side).

Does this base have teflon pads or a lazy susan bearing?  Watch the upper board (called the azimuth board)  carefully in the day when you rotate the scope.  Is it flat or warped?

Is there a tension adjustment bolt in the center of the azimuth board?   Have you loosened it?

 

I tried contacting a local astronomy club but got no response.   Try again, this is not a professional help desk with service now ticketing system running.  Your request may have just gotten lost, or the ball dropped.

There was no extension tube when I bought it, but the scope was used. Its probably 10+ years old. I'll try the two things you mentioned.

 

I have upgraded teflon pads on the bottom board. Both the upper and the lower boards are nearly perfectly flat. I have an AstroSystems adjustable pivot mount. It is definitely not too tight. I suppose I need to just buy a teflon ring for the upper board.

 

I will definitely try to contact the club (Buffalo Astronomical Assoc.) again. Really hoping I don't have to haul the scope down to North Java to get someone to look at it.

Edited by gdeihl, 06 February 2025 - 12:47 PM.

[SoCalPaul]

Back in April of 2021 I purchased a 10" Zhummel Dobsonian telescope. I got a lot of good advice concerning questions I asked, but I'm now struggling with whether or not to continue trying to make this telescope work for me. Everything in the eyepiece is out of focus. I've tried collimating, but it made no difference. I probably shouldn't have taken the scope apart and cleaned the primary mirror without checking this first (it was cloudy for weeks after I bought it and got impatient to do something with the scope). I tried contacting a local astronomy club but got no response. I still haven't gotten the issues with my base resolved (sticks turning side to side). I put the scope aside in late 2021 after being frustrated for way too long and haven't touched it since besides taking it upstairs to a spare bedroom and putting a cover on it.

 

Before I give up and sell this telescope does anyone live in the Buffalo, NY area that can take a look at what is going on with it and help get my problems resolved?

Frustration is not unique to beginners, trust me. I had a bad night due to equipment failures a week ago, grr.

 

My opinion is that your next best action is to get in-person assistance from someone with experience, despite the lack of response from your local astro club. See if they have a FB group, as these tend to be more active than websites or mail lists, in my experience.

 

I hope you don't give up and are able to get the assistance needed without having to do more somersaults. Once you get that scope performing, I think you will feel that the effort was worth it, that the sky's treasures are wonderful to behold.

 

Maybe also start a new post here on CN titled something like, "Need help in Buffalo area". I feel confident that there are CN members in your area, and you might strike gold if one of them is willing to meet up.

 

Clear skies,

Paul

[SeattleScott]

Typically the best way to interact with a local astronomy group is to attend one of their meetings. Especially if you live a ways away, they aren’t necessarily going to be inclined to make house calls. It isn’t really fair to expect them to travel to meet you considering they aren’t getting paid for their service. But if you show up with your scope, they will typically be happy to assist.

Your scope may well be worth $500 or so. Certainly it should have an extension tube. That’s a standard accessory for a Dob. If you can reach focus by pulling the eyepiece out of the focuser a bit, then an extension tube will work. So you can look into that. But ultimately, if that doesn’t seem to be the issue, it might be worth traveling to North Java if that’s what it takes to get hands on expert advice for free.

[Inkie]

If you can't get it to focus, and you have it collimated, then there's something wrong/off with the distance to the focal plane, and you're not reaching it.  So, as others have opined, you are missing a tube, maybe four inches in length, that you insert into the focuser.  Then, when you insert your eyepieces, they will come to focus somewhere along those extra four inches.  It will work!!  Your journey, so far, hasn't gotten you to the 'sweet spot'.  It's there, just ahead of you, in the shadows. 

[dmgriff]

As previously mentioned, if it has a low profile focuser, you need a 2in diameter 2in extension. About ~30usd.

 

Examples:

 

https://agenaastro.c...-extension.html

 

https://www.surpluss...tem/l3838d.html

Edited by dmgriff, 06 February 2025 - 01:35 PM.

[Ionthesky]

You might want to try an email to the membership chair, if you haven't already.  Here's a link to the membership page for the BAA:

https://www.buffaloa...ecome-a-member/

 

Dennis might respond to the email quicker than the phone call.  I have no idea who that phone number goes to.  

 

It looks like there's a club meeting next Friday.

 

Good luck!  (and I agree...the focus problem is most likely due to the lack of an extension.)

[sevenofnine]

Welcome Back!  

 

Do you have a collimation cap? Take a cell phone shot through the tiny hole and post the results here. There are several collimation experts on this forum that can help you decipher the problem(s). Dobs are really pretty simple scopes but it does take a little time and patience to sort it out especially if the scope is used. You just don't know what the previous owner did to it. Good luck! 

 

 https://agenaastro.c...t-eyepiece.html.

[HenkSB]

You bought the scope used and the owner kept the extension piece that you desperately need to get it to focus.

[A Star Geezer]

gdeihl

  Don't get discouraged It'll get fixed. It might help if you explained how you collimated the scope. Seven had a good idea about a picture of the mirrors through a collimating cap, place a piece of white paper opposite the focuser it highlights things.  I'm NOT an expert I had my apertura  10 inch dob about 4 months and I have the new scope  curse of weather. Mine came with the extension tube that is not needed. What eyepieces came with it. Look around and find the posts about collimating the scope. God luck

[A Star Geezer]

https://www.cloudyni...y-focuser-tube/

Try looking here Lot of good info and helpful people 

Edited by A Star Geezer, 06 February 2025 - 03:01 PM.

[Dave Mitsky]

A 35 mm extension tube helps bring images into focus when used with different eyepieces or camera setups.

https://www.highpoin...ce caps of Mars.

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[SoCalPaul]

You bought the scope used and the owner kept the extension piece that you desperately need to get it to focus.

A number of folks have now pointed to a missing extension tube. Fingers crossed, let's hope it's that simple for the OP!

 

gdeihl - if you are a prime member, you can have one overnight: https://a.co/d/1oWF3BG

 

All the teeth-gnashing and hair-tearing, when after all it might just be a small, missing piece. Life can be like that, sometimes.

 

Paul

[A Star Geezer]

here's video explaining how the mirrors work together and how to collimate them

https://www.youtube....?v=Xzus4oA8Ses 

[gdeihl]

Maybe also start a new post here on CN titled something like, "Need help in Buffalo area". I feel confident that there are CN members in your area, and you might strike gold if one of them is willing to meet up.

I'll try that after I attempt some of the suggestions made here.

[Barlowbill]

I have an 8" Dob so I don't have this problem.  Does he need a 35mm ort a 50mm Extension Tube?

[Mark F.]

Before I give up and sell this telescope does anyone live in the Buffalo, NY area that can take a look at what is going on with it and help get my problems resolved?

You've gotten some good advice here.  If you're still stuck and you'd like someone to check out your scope, I live in the Buffalo metro area and have a 12" GSO dob, so I'm familiar with these telescopes.  PM me.
 

[RiderRoy]

My XT10 needed a 2" 35mm extension tube to be able to reach focus. Like has been said, get an extension tube and you'll be good to go. That's a very good telescope you have. You will enjoy the views through it. 

Mine came from Orion. Since that's no longer an option for anyone anywhere.....   A quick amazon search turns up several 50mm and 35mm options. 

 

Get that focuser working and get out under the night sky! 

[astrohamp]

Mark F: have you been able to find the mirror(s) focus point with a paper screen held outside an empty focuser with the OTA pointing out a window (or outdoors) at distant high contrast object (like tree limbs in open sky) some hundred yards away or more?

 

Advantage to being inside is not cold and darker ambient light around the OTA/EP to see the projected image on the screen.  Your hand will also work BTW.

 

Let us folk know what you find.

[SeattleScott]

I have an 8" Dob so I don't have this problem. Does he need a 35mm ort a 50mm Extension Tube?

Don’t know, he would have to measure and see.

Basically you pull the eyepiece out of the focuser until it reaches focus. Then you measure how far the gap is.

[grace]

I had the same problem on my 8in dobson, objects wouldn’t come into focus. The extension made the trick. Now all eyepieces work well on all types objects, I just cannot het my highest magnification one on the moon, I should probably remove the extension for that…

[Ranger Tim]

How did you clean it? Describe your process. Mirror coatings are very vulnerable to any aggressive efforts.

[A Star Geezer]

Here is an example of what Sevenofnine suggests