Orion XT10 problem

[watersblue]

After buying my xt10 with a fairly tatty mirror, I am wondering whether it's such a good deal. The mirror has numerous spots/splats on it, but looks in fairly good shape. However, when trying to use it on the moon woth a 10mm ep, it looks a bit blurred. It's okay with the 32mm and 25mm ep I have, but the 10mm is not good. There is better clarity on my sw200p dob. Is it just the fact that the primary has these marks on? Would I be aleto just get it recoated? The secondary seems to be in good shape.

Thanks. Please offer me some advice!

[NGC 1502]

We feel your pain if you are disappointed with your XT10.

First check I'd make would be collimation.   If that's off, would seriously affect the views, more so at higher magnification, which is what you have found.

Another issue could be cooldown, more relevant if the scope is stored in a warm house, then taken out into the much colder outdoors.  Maybe 25 - 50 mins for cooldown with a 10", but difficult to be precise on that.

I'd doubt if the issue is caused by a dirty mirror.  Maybe you could post a pic ?    If it's VERY dirty, a careful wash could help, but please don't be too surprised if cleaning doesn't make a big difference to the views.

Let us know how you get on, and perhaps others will have more info to help.

Regards, Ed.

[Avocette]

Any idea what the splats and spots are and do they cover a significant area of the mirror? Before going as far as recoating, would you be prepared to give it a careful cleaning finishing up with distilled water rinse? (nice video on YouTube of Steve Richards (steppenwolf) doing the business).

[John]

I wonder if someone has tried to clean the primary, perhaps prior to the sale, and done so rather clumsily giving it some micro scratches ?. Something like that could reduce the sharpness at higher magnification ?.

You can get mirrors re-coated if careful cleaning will not do the trick.

[laowho]

We feel your pain if you are disappointed with your XT10.

First check I'd make would be collimation.   If that's off, would seriously affect the views, more so at higher magnification, which is what you have found.

Another issue could be cooldown, more relevant if the scope is stored in a warm house, then taken out into the much colder outdoors.  Maybe 25 - 50 mins for cooldown with a 10", but difficult to be precise on that.

I'd doubt if the issue is caused by a dirty mirror.  Maybe you could post a pic ?    If it's VERY dirty, a careful wash could help, but please don't be too surprised if cleaning doesn't make a big difference to the views.

Let us know how you get on, and perhaps others will have more info to help.

Regards, Ed.

As Ed notes, the moon is bright and a dirty mirror here wouldn't cause the blur you're experiencing. After trying the other things suggested, look to see whether the blur changes or remains constant. If your 10mm simply continues to refuse to focus, try a mask to check for a turned down edge. If this improves things, there's your easy fix.

[Peter Drew]

I have a 6" and 8" XT Dobsonian, both have excellent optics, I would expect the 10" to be of similar quality. Hopefully the problem will be elsewhere.