Having trouble with Hotech

[Rob L]

Hi,

I bought the Hotech with my new scope as general opinion seems to be it makes the collimation process a lot easier.

The first time I tried it, the secondary was a tiny bit out which I corrected and adjusting the primary was even easier, great I thought, why was I worried about collimation!

However my problems started a few days later when I decided to check it again... the secondary reflection in the primary was out by about 5mm which I was surprised about, but quickly adjusted it again. Sorted the primary and was happy, until I decided to put the laser back in and check again.

Every time I put the Hotech in I get a different result. I tried about 5 times in a row.

If I secure it in the focuser as tight as possible (really tightening the compression ring to its max) the dot is fairly consistent within the centre dot on the primary, but the position of the laser on the crosshairs for primary mirror adjustment is always in a very different area of the crosshair.

One other thing I've noticed is if I tilt the scope from 45o and above the dot stays in the same spot on the crosshairs but if i tilt the scope below 45o the position moves, is this normal?

Hoping someone can help with this, I'm really not sure if its me, the hotech, the scope or a combination of all three.

[acey]

Test your scope by looking at an out-of-focus star, both inside and outside of focus, using high magnification. If you are well collimated (and the air is steady) then you will see a dark spot exactly in the middle of a series of perfectly circular rings.

It is possible for a scope to go out of collimation when moved in altitude because the primary mirror and other components are shifting under their own weight. If the difference is enough to be noticeable with a star test then you've maybe got a problem (e.g. the primary is not sufficiently supported), otherwise not.

It is also possible for lasers to give misleading results: again, check using the star test.

[Rob L]

Thanks for replying acey. I did do a star test of sorts, centred on a star and then defocussed until I had a very fat doughnut image, the centre of the doughnet was very slightly off centre which is what made me initially recheck with the Hotech.

My main concern is removing and reinserting the Hotech several times in a row I get a very different position on the crosshairs.

I made an error in my initial post, it is below the horizontal the laser shifts on the crosshairs, which I suppose makes sense as the weight is being shifted from the back to the front?

[Orion_the_Hunter]

Hi Rob, I don't know a lot about collimation but mabe this will help.

Laser Collimator Collimator

Regards, Ed

[Ant]

I made an error in my initial post, it is below the horizontal the laser shifts on the crosshairs, which I suppose makes sense as the weight is being shifted from the back to the front?

Do you mean that when the scope is pointing at the ground it changes...? If so I wouldn't sorry too much about that as in normal use you'll never be in that position.

All the Cheshire's, Hotech's, lasers' etc are no substitute for a star test - get it as close as you can with your preferred method and then star check and refine.

Cheers

Ant

[Rob L]

Hi Rob, I don't know a lot about collimation but mabe this will help.

Laser Collimator Collimator

Regards, Ed

Thanks Ed, I haven't checked if the actual collimation on the laser is out yet.

I've googled it and it's very rare for a Hotech to leave the manufacturer out of collimation, but definatley worth checking.

[Rob L]

Do you mean that when the scope is pointing at the ground it changes...? If so I wouldn't sorry too much about that as in normal use you'll never be in that position.

All the Cheshire's, Hotech's, lasers' etc are no substitute for a star test - get it as close as you can with your preferred method and then star check and refine.

Cheers

Ant

Agreed, I probably won't have much call for viewing at an angle below 0 degrees

[Rob L]

Phew!

Recipe for a happy bunny: 1 x collimation cap, 1 x cheshire, 1 x AstroBaby's guide

20 minutes later, perfectly (close enough for me) collimated scope.

Thank you Astro Baby for your brilliant guide.

1 x laser consigned to the bin!

[acey]

You've done the right thing. Laser is handy for aligning the secondary (I use mine for that) but for the primary its a Cheshire and star test every time.