altair astro finder focus problem

[nutrocker]

HI,

I have a real problem with my Altair astro 10 x 60 finderscope in that i cannot focus the illuminated crosshairs and also focus on infinity at the same time. A previous member mentioned reversing the crosshairs  but i cannot find this thread. Could anyone help me with this by maybe advising another solution or more details on how to flip the crosshairs ?

 

thanks

[MarkAR]

I had the same issue and remember that thread. I think you unscrew the tube bit, then the retaining ring and flip it.

In the end I didn't do it because when the stars are in focus the cross hairs show as double so that you can see the star dead centre.

[nutrocker]

Thanks for that,seeing the crosshairs double is a good point and taking the retaining ring out makes me nervous, but i would like to get to the bottom of it.Altair responded to my question as i have only just purchased it but they just state obvious  which is not working. I get the impression from correspondance that they think i don'know how to work it,which i do.

Still, any ideas i would love to hear.

[Mark at Beaufort]

@nutrockerI own both the Altair 80mm and 60mm finderscope and they both use the same arrangement for focusing the telescope and the eyepiece.

Sometimes a new Altair helical focuser could be stiff so this is what I recommend.

• Remove the eyepiece completely
• Twist the helical focuser - when screwed tight its at infinity when you screw it out (about half an inch) its at close focus. Move it up and down then screw it right in.
• With the eyepiece out use its focusing ring to get the cross hairs sharp then replace the eyepiece into the diagonal.
• View a distant TV aerial or similar and slightly adjust the helical focuser to obtain a sharp image - if it needs it.. Don't touch the eyepiece.

I would recommend you don't touch the the glass screen with the cross hairs although in the future you may want to remove small dust particles.

Hope this helps.

[nutrocker]

Hi Mark,

thanks for your advice. I did try this last night but alas it made no difference. I have been offered a refund  but weirdly i still think that despite this irritating problem i will hang on to it. That is not to say i would not  like to hear of a solution,because at £170 it should be perfect !

 

Thanks,

 

Rob

[Mark at Beaufort]

53 minutes ago, nutrocker said:

Hi Mark,

thanks for your advice. I did try this last night but alas it made no difference. I have been offered a refund  but weirdly i still think that despite this irritating problem i will hang on to it. That is not to say i would not  like to hear of a solution,because at £170 it should be perfect !

 

Thanks,

 

Rob

Rob that sounds very frustrating. I know that sometimes, especially on the 60mm finder, the rubber focusing ring seems to slip and does not move. I sometimes use the eyepiece securing bolt to get fine focus rather than using the focusing ring. Have you another EP that you could try? When I star hop with the finder I sometimes use a different eyepiece. I know that some of my EPs need to twisted out so easier to focus. 

[Louis D]

I'm confused.  Doesn't the eyepiece have helical focuser on it to bring the reticle into focus?  I'm guessing it's the ribbed ring right below the eye cup and just above the illuminator ring.  Does it not turn?  If not, you've got a defective eyepiece.  If it does turn, focus the reticle first and then use the knurled rubber helical focuser on the diagonal to focus the objective onto the reticle.

I found a description of the eyepiece by itself here.  It says in the description "Can be focused by twisting the top portion of the eyepiece".  That would refer to the ribbed section.  Grab the illuminator ring in one hand and the ribbed section in the other and give it a good counter-clockwise twist first to see if it will go up.  If it appears to be all the way up, try twisting it in the opposite direction.  Pretty much all reticle eyepieces, even the cheapest ones, are focusable.

[MarkAR]

Thats the one I have as well. 

Considering there seem to be a few out there with owners all having the same problem, it is either put together wrong or it is supposed to be off.

If its supposed to be off, then with the reticle sharp the star is blobbed up to possibly a doughnut and the crosshairs can mark the centre of the doughnut. Or a sharp star visible in the centre of the fuzzed crosshairs.

I'm not sure if even Altair will know what its supposed to be doing.

[nutrocker]

Thanks for all your inputs.In a nutshell when the crosshairs are finely focused the eye piece is just slightly out. there is no more travel left. There seems to be no way around this. I think i am going to ask Altair to send me a replacement EP and take it from there.

[Louis D]

47 minutes ago, nutrocker said:

Thanks for all your inputs.In a nutshell when the crosshairs are finely focused the eye piece is just slightly out. there is no more travel left. There seems to be no way around this. I think i am going to ask Altair to send me a replacement EP and take it from there.

Do you need to wear eyeglasses?  Perhaps try focusing the crosshairs while wearing glasses to see if you've reached the diopter limit of it's built-in focuser.

[MarkAR]

55 minutes ago, Louis D said:

Do you need to wear eyeglasses?  Perhaps try focusing the crosshairs while wearing glasses to see if you've reached the diopter limit of it's built-in focuser.

Wouldn't be this, he eyepiece definitely has one focus point for the stars and another for the crosshairs.

[Louis D]

2 hours ago, MarkAR said:

Wouldn't be this, he eyepiece definitely has one focus point for the stars and another for the crosshairs.

Oh, I think I see now.  The reticle etching isn't in the same plane as the field stop/focal plane.  I agree that it sounds like the factory installed the reticle upside-down.

[nutrocker]

I have asked Altair for a replacement EP and am at present waiting for a response. Your comments are appreciated.

[Mr F]

To resurrect this topic in case anyone else searches for this problem....

I have just bought the Altair 60mm finderscope and have found exactly the same focus problem that the OP had.

I have been advised by the shop that Altair have advised that the focus allows +/- 5 dioptres which should suit most users.

I assume that the inference here is that it's my eyes that are 'at fault' not the scope.

I have no issues with any other optical equipment that I own.

So I assume that if anyone else has this issue, it is inherent in the design of the eyepiece.

Oh and hello everyone! I'm new here, based in South Lakes Cumbria UK

Edited November 9, 2020 by Mr F
Additional

[nutrocker]

Hi,

 

Sadly you are now a member of the altair  finderscope dissatisfied club. I too have no problems with any optical pieces except this.

i am currently awaiting to see if anyone can give me a detailed explanation as to how to turn over the etched reticle to cure the problem.

Watch this thread to see maybe if it is of any help to you.

 

All the best

Edited November 10, 2020 by nutrocker
wrong words

[Geoff Frost]

I am in the UK. I have exactly the same problem. I think the main tube is about 5 to 6mm too long. This would bring the main focus into some sort of mid position. Could skim about 1mm off eack end of the main tube. This would reduce the threads but they may still function. Do I give it a try????

Oh I have two tubes and two eyepieces. One set is slightly better than the other but both are screwed right down to the minimum.

Edited November 24, 2020 by Geoff Frost
additional comments

[Geoff Frost]

So, just carried out some measurements and there is only 1mm max of spare thread which still makes the focusing tight.

Plan B. Cut the tube and insert a spacer.

[Geoff Frost]

Not sure if this will work but I will upload the drawings for comment.existing.pdf

spacer.pdf modified tube.pdf

[Geoff Frost]

So this is my solution to get the finder scope to focus. The result works perfectly. I now have plenty of focus adjustment after focussing the crosshairs. I removed about 5 or 6mm from the tube length and the joined it back together again.