Celestron Astromaster 90AZ telescope blurry

[Mogra]

Hi,

I just bought a Celestron Astromaster 90AZ telescope. Trying to set it up.

Went out and pointed to a electric pole about a mile away. Tried to focus using a 20mm eyepiece.

But it is out of focus and blurry

unable to get a sharp image

Any suggestions OR tips ?

Thanks !

[Second Time Around]

Have you put the star diagonal in?  This is the L-shaped accessory that comes with the scope.  The eyepiece then goes into the star diagonal.

[RT65CB-SWL]

Hi @Mogra and welcome to SGL. 

Agree with what @Second Time Around says above. My TeleVue Ranger will not come into focus if I do not use the star diagonal.

You will/should find the image right way up and left/right or east/west are reversed. This is 'normal'. Some telescopes, i.e. 'Newtonian' reflectors, South is up.

[Mogra]

yes have the diagonal. Unable to get sharp focused image. Does wind and cloud affect the viewing.

Also the red dot scope finder has stopped working. I changed the batteries still no luck .

 

Thanks

 

Edited December 22, 2020 by Mogra

[happy-kat]

Have you tried slowly winding the focuser all the way in then all the way out to see when focus is reached. Also if you swap eyepiece then you may need to adjust focus again.

[Mogra]

I think my focus tube is not moving out all the way. It extends out for a bit and  then the knob keeps rotating with clicking noise and nothing moves.

Edited December 23, 2020 by Mogra

[DaveL59]

any chance you can post a pic of the focuser at its furthest out and as you have it set up for use?

My LT70AZ drawtube gets focus at around 2-inches and can go much further. This was on some treetops around 150m away.

Not sure if yours has a locking screw as mine doesn't, but there's no clicking when extended. Almost sounds like you've racked it back off the end of the rack but I don't think that's possible from the design as on mine the end of the rack gearing is an un-machined/formed block which would act as an end-stop. Is the focuser very slack to turn or quite firm/tight?

Edited December 23, 2020 by DaveL59

[Mogra]

Thank you all for taking the time to respond to my queries.

Here is how the focuser looks in fully in and fully out position. Not much room for adjustment as you can see.  I can move it easily just 3 turns. Its not slack or tight. moves fine.

Thanks again for your time and help!

 

Edited December 23, 2020 by Mogra

[DaveL59]

ouch that doesn't look like much travel at all, a different focuser to the one on mine so hopefully someone who has direct experience with one of these may be along to advise further. For sure you'd need the diagonal or an extension tube.

Are you feeling that it gets closer to focus as it hits the furthest out it will go?

If that's the case what you could try is unscrew the lens off the barlow and fit that into the scope first as an extension, then the diagonal and eyepiece and see if that'll reach focus.

[Mogra]

Not really 

4 minutes ago, DaveL59 said:

ouch that doesn't look like much travel at all, a different focuser to the one on mine so hopefully someone who has direct experience with one of these may be along to advise further. For sure you'd need the diagonal or an extension tube.

I do have a diagonal and am using it though its not in the pictures I posted.

Are you feeling that it gets closer to focus as it hits the furthest out it will go ? Not really. Took it out last night to see the moon and i could only see a shiny bright light. Nothing like images people are posting.

If that's the case what you could try is unscrew the lens off the barlow and fit that into the scope first as an extension, then the diagonal and eyepiece and see if that'll reach focus.

 

 

[Alan64]

24 minutes ago, Mogra said:

Thank you all for taking the time to respond to my queries.

Here is how the focuser looks in fully in and fully out position. Not much room for adjustment as you can see.  I can move it easily just 3 turns. Its not slack or tight. moves fine.

Thanks again for your time and help!

You need a star-diagonal, for use at night.  The telescope came with an Amici, erect-image diagonal.  The Amici diagonal is provided so that you can use it during the day for terrestrial objects, and at night, but it's primarily for use during the day.  A star-diagonal is for use only at night, and is the ideal for that...

I have that same oddly-designed focusser on my "AstroMaster" 70EQ, and I despise it.  I'm always looking for a conventional, traditional replacement for it, but I haven't found one yet.

[DaveL59]

3 minutes ago, Alan64 said:

 

I have that same oddly-designed focusser on my "AstroMaster" 70EQ, and I despise it.  I'm always looking for a conventional, traditional replacement for it, but I haven't found one yet.

What's the travel on the focuser like tho Alan? As short as the OP's pics?

I'd expect it should hit focus with the erecting diagonal, ok not the best for stars but focus should be possible and this seems to be the problem they are having.

[Mogra]

I think this is a pinion /rack problem. Will be sending scope back to Celestron for repair / replacement.

[Alan64]

25 minutes ago, DaveL59 said:

What's the travel on the focuser like tho Alan? As short as the OP's pics?

I'd expect it should hit focus with the erecting diagonal, ok not the best for stars but focus should be possible and this seems to be the problem they are having.

Hmm, I was wondering upon first reading of this thread if there was something wrong with the OP's draw-tube, perhaps broken rack-teeth, or other.  But then, my own is a 70mm at f/13; the OP's a 90mm at f/10.  Still, that is awfully short if that's far as the draw-tube can be racked outward.  It does seem to warrant a disassembly of the focusser for inspection.

Oh, I was under the standing that the OP did not have a diagonal at all; the kit used, in other words.

Edited December 23, 2020 by Alan64

[Alan64]

In addition, elsewhere within another site, a star-mirror diagonal would not come to focus with that 70mm f/13, and I had replied that a star-prism will with my own.  If a star-diagonal is acquired in this instance, to play it safe a star-prism is suggested.

[DaveL59]

16 minutes ago, Mogra said:

I think this is a pinion /rack problem. Will be sending scope back to Celestron for repair / replacement.

does sound like the best option considering it's a new scope so warranty should cover getting it sorted.

[Andy0306]

Have you tried gently pulling on the draw tube as you turn the focuser? If there are a couple of teeth missing, it may re-engage and bring the tube fully out.

[Mogra]

here are the rack pinion pictures. Looks like that may be the issue. I could manually pull out a little more.

 

Edited December 23, 2020 by Mogra

[DaveL59]

yeah its plastic unfortunately so if teeth have been lost then warranty replacement will be the way to go. Given the time left to the holiday I doubt they'll be able to do anything nor will the postal services, so if you can now reach focus, may as well have a couple days use out of it before sending it back...