SCT Collimation Service

andeelym · Post by **andeelym** » Mon Jul 25, 2011 11:01 am

Hi,

Anyone know where can I get help with SCT collimation? I am willing to pay a reasonable amount for the service as well.

I do not have a tracking mount yet, so its a bad pain to do star collimation. I bought a Hubble artificial star but I could get enough back focus and my house is not big enough to do the collimation indoors. Am thinking of buying the Hotech Advanced CT Laser Collimation system but 450USD is a big hole in the wallet for me to patch. I do not mind renting it from anyone who has it.

Any help is appreciated. Thanks for reading!

Gary · Post by **Gary** » Mon Jul 25, 2011 4:14 pm

Hi andeelym. I don't mind helping out if you trust my beginner SCT collimating skill. At least I can provide a helping hand to hold your artificial star device at a greater distance outdoor. Free of charge of course.

I have tried collimating my 8" SCTs using the manual porta mount using real stars. Tedious to do alone, but it is a fun and rewarding experience after you see the same objects with a better collimated SCT.

Do not buy the Hotech system. Not worth the money. For a little more, you can buy a brand new WO 72mm refractor with minimal collimation issues! How to psychological justify for a $450 collimating device? LOL

(1.00 USD = 1.20803 SGD now!)

I have observed with my Mak 5" at Marina Barrage. There are many distant red light bulbs on top of tall buildings that gave nice airy discs. Also saw a daytime sunlight reflection of the same type of light bulb at a distant HDB block near my place which produced the same airy discs too. Of course, those daytime ones are very dependent on the cloud condition compared to those at night. So perhaps can do some collimation using those distant red lights.

Again, best option is to bring your scope to a dark and clear Milky Way sky location. You can afford to collimate it for hours on real stars and still have plenty of time left for observing.

You can PM me your contact details if you are keen.

kayheem · Post by **kayheem** » Mon Jul 25, 2011 4:21 pm

Hi,

Forget the collimation service. What if it is bumped out of collimation on your way home? :-(

One way to get around the problem of not having enough backfocus, is to use a small shiny sphere e.g. Christmas tree decoration or smooth steel ball bearing. Mount this shiny sphere onto a matte black background as far from the scope as you can get. Shine a torch (need not be those super-bright Xenon type) on the sphere. View the sphere through the scope. Because of the small radius of the sphere, the image is virtually far away.

Hope this helps.

andeelym · Post by **andeelym** » Mon Jul 25, 2011 5:25 pm

@Gary: Thanks for the offer, well, the thing is, I couldn't afford much time to be away from home for my hobby. Can only view from home, at least until my kids grow up in a couple of years. (Haiz...).

Do you also mean that distant lights like those red airplane warning lights can do too? I am planning to buy the Hotech SCA laser collimator, not the advanced one, so that I can easily re-collimate after I "remember" the position after a good collimation for my 8" SCT.

@Kayheem: I do not really understand using the ball bearing even though I read about it. I am unable to even achieve focus on the artificial star due to the short distance at home, then how so will the ball bearing help? I am assuming that the ball bearing will produce a "big" shine that will be hard to focus on.

Or do you mean that bigger light sources are better, rather than smaller ones?

Haha, to prevent collimation from going off, I even plan to stick scotch tape at the bob knobs so that they will not be turned.

Post by **zong** » Mon Jul 25, 2011 6:31 pm

I'm not sure scotch tapes will work. Anyway, collimation is not hard to learn, and not hard to do after you take a little time to hone the skill. If your kids are <4, you can probably try this after they're asleep. If they're 4-8, you can bring them to ECP, make them play whole day and conk out in the tent at night, then do it. So there's always time to learn

Also, how well you want the collimation to be depends on you. If you don't have time, a simple 10-15min collimation can already give you wonderful results. I'm not sure if you can ever achieve "perfect collimation", so to me, half an hour of decent collimation is enough. I'm out there to look at stars, not defocussed rings of light!

Gary · Post by **Gary** » Mon Jul 25, 2011 8:07 pm

Hi andeelym. No worries. You are welcome. I assume when you say "can only view from home", it means you can view some stars through a opened window or door or be able to do so at a very nearby common corridor or partially open space.

If that is the case, why don't you just collimate with real stars when the nights are relatively clear enough from home? For example, Vega and Arcturus are still visible for the past few nights for a relatively long period of time though the weather was hazy overall.

Personally, from a visual observer point of view, I don't foresee we can complete any Messier Marathon in Singapore for many years to come (forever?). So I don't see any huge significant advantage of collimating my SCTs way beforehand. And like Zong mentioned, it is not that hard to learn collimation. After a few tries, you will get the hang of it and it will not take up too much of your observing time. Thus, you can even do it quickly for every session and not to worry about the collimation going off in-between observing sessions and also taping up the bob's knobs which is not effective and really spoil the look of those cool knobs.

Regarding the red light collimation, why not give it a try. If it works for you, it may save you some cash from buying a collimator.

Since you do not have much time for this hobby and can mainly observe in Singapore, perhaps a quality fast-setup refractor system might be more suitable for you if you do not already own one by now. Even when your kids grow up and you do find more time for this hobby, a quality refractor is still a keeper for rich wide views of clear dark skies among other things it can do well.

Btw, this is a SCT collimation guide by Rod Mollise (aka Uncle Rod) for those who are interested in this topic:
http://skywatch.brainiac.com/collimation.pdf

Post by **acc** » Mon Jul 25, 2011 8:40 pm

I use aircraft warning lights for collimation too and they work fine. Collimation is easy once you get the hang of it and there's really no need to buy an expensive laser collimator.

kayheem · Post by **kayheem** » Mon Jul 25, 2011 10:16 pm

andeelym wrote: @Kayheem: I do not really understand using the ball bearing even though I read about it. I am unable to even achieve focus on the artificial star due to the short distance at home, then how so will the ball bearing help? I am assuming that the ball bearing will produce a "big" shine that will be hard to focus on.

1) mount a ball bearing on a matte black surface.
2) aim your scope at the ball bearing
3) while in the dark, shine a flashlight at the ball bearing
4) focus on the light reflected from the ball bearing and not the ball bearing itself. The reflected point of light is virtually very far away.

Hope this helps.

P.S. Start collimation at low power. Increase the power and collimate at focus, observing the diffraction rings and not the de-focused rings.

cloud_cover · Post by **cloud_cover** » Tue Jul 26, 2011 12:53 am

kayheem wrote:The reflected point of light is virtually very far away.

Could you explain this?

kayheem · Post by **kayheem** » Tue Jul 26, 2011 8:18 am

You know those convex mirrors that are used at blind spots for traffic?
The image you see is small and far away. It is the same principle, except exaggerated effect. The reflected light appears as a point very far away. Remember, you are focusing on the light and not the ball bearing.