Astro essentials focuser issue

[tich]

Hi everyone, I bought an Astro essentials focuser for my 250P as an upgrade to the Skywatchers Crayford as in my view they've never been any good. I fitted it & all seems fine I also fitted a new spider vane & mirror clip mask to then came the fun part. Whilst the focuser feels much better than the stock one how do you align it with the secondary so you can see whole of the primary using a collimation cap? Mine looks miles out & I have no means of adjustment? I know I could see it all with the stock focuser when I've set it up in the past but with this there's about a third out of view with this one.
Any ideas or help would be appreciated thanks.

https://www.firstlightoptics.com/astro-essentials-focusers/astro-essentials-v2-2-dual-speed-low-profile-crayford-focuser-for-newtonian-telescopes.html

 

[CraigT82]

Don’t you just need to rotate the secondary a bit and adjust it’s tilt with the three secondary adjustment screws? 

[bosun21]

When I changed the focuser on my 250 Synscan dobsonian to a Baader Steeltrack I found that using a concentre (concenter) to be invaluable in centering the secondary and setting the tilt. Saves a lot of time and frustration.

[tich]

7 minutes ago, CraigT82 said:

Don’t you just need to rotate the secondary a bit and adjust it’s tilt with the three secondary adjustment screws? 

The rotation is as good as I can get it so when looking at it I can see top, bottom & the right hand side of the primary but not the left when looking at the secondary if that makes sense. 

[alacant]

Hi
Perhaps send us a photo looking through the cap? Better, through a Cheshire sight tube. Even better if the latter has cross hairs.
 

[Stuart1971]

Isn’t there normally a rubber O ring under each of the 4 focuser unit fastening screws, so you can adjust the whole thing a small amount when fitting…?

Or am I thinking of something else, I’m sure I have seen this recently in a YT video of someone replacing one of these focusers…🤔

[tich]

23 minutes ago, alacant said:

Hi
Perhaps send us a photo looking through the cap? Better, through a Cheshire sight tube. Even better if the latter has cross hairs.
 

I'll try & get a picture when I get home although I fear it may not be easy to do, I still managed to collimate it but the alignment isn't good as mentioned.

[tich]

12 minutes ago, Stuart1971 said:

Isn’t there normally a rubber O ring under each of the 4 focuser unit fastening screws, so you can adjust the whole thing a small amount when fitting…?

Or am I thinking of something else, I’m sure I have seen this recently in a YT video of someone replacing one of these focusers…🤔

I think stock Skywatcher focusers have the O rings but they also have tilt screws for adjusting so not really sure what they're used for. I may try using a washers as shims to see if I can adjust it that way but doesn't seem ideal.

[alacant]

Yeah. Flexible washers. In a focuser. What a wonderful idea!

2 hours ago, tich said:

not be easy to do,

Just hold your phone up to the central hole, making sure it's as square as possible.

3 hours ago, Stuart1971 said:

rubber O ring under each of the 4 focuser unit

Thankfully, not. There are a total of 7 bits of rubber which need to be removed.

[Stuart1971]

1 minute ago, alacant said:

Yeah. Flexible washers. In a focuser. What a wonderful idea!

Just hold your phone up to the central hole, making sure it's as square as possible.

Thankfully, not. There are a total of 7 bits of rubber which need to be removed.

Well you are clearly a bit clueless to how some of these focuser work, but I am not going to waste my time explaining as you have made your mind up…👍🏻

[Kon]

You need to give us more info on how you are collimating.

I have the same focuser on my 300P. I had similar issue but it was down to wobbly Cheshire. See p3 , 4th post down.

 

 

 

Edited August 10 by Kon

[tich]

36 minutes ago, Kon said:

You need to give us more info on how you are collimating.

I have the same focuser on my 300P. I had similar issue but it was down to wobbly Cheshire. See p3 , 4th post down.

 

 

 

Ah very interesting thanks for the link I have changed the spider vanes on my scope which are more substantial than the originals so maybe that's put something out along the way? I'll check it again over next week, one thing I did notice is when you bolted the vanes onto the tube the bolts were smaller than whats originally fitted so I think I pushed the vanes down into the tube so it was as flush as it could be. For the price of the "upgrade" you'd think they would have got that part right.

This is the kit I fitted;

https://www.firstlightoptics.com/misc/backyard-universe-secondary-mirror-spider-for-sky-watcher-250mm-newtonian-telescopes.html

[bottletopburly]

When I changed spider and focuser I found the focuser was misaligned to ota , took me ages to work out the issue only with the Ocal I sorted it as I collimated and recollimated and could not align the doughnut to the crosshairs on the Ocal , luckily the Steeltrack you can tweak the drawtube, once I did that collimation was bang on , btw if you ever need to borrow tich im in next town 👍

[tich]

3 hours ago, bottletopburly said:

When I changed spider and focuser I found the focuser was misaligned to ota , took me ages to work out the issue only with the Ocal I sorted it as I collimated and recollimated and could not align the doughnut to the crosshairs on the Ocal , luckily the Steeltrack you can tweak the drawtube, once I did that collimation was bang on , btw if you ever need to borrow tich im in next town 👍

Thanks for the offer I may take you up on that, sadly I don't have a steeltrack I went for the Astro essentials which has no way of adjusting any tilt, however I'm hoping by moving the secondary I'll be able to get to see the whole of the primary via the collimation cap as it should be pretty square onto the tube, but then I guess we'll see when I next go into the observatory to fettle it lol.