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How do I tell if my telescope needs collimating?


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I have recently purchase a celestron 6se and although I can see saturn fairly well (cannot see any banding or the cassini division), I am finding it almost impossible to make out any deep sky objects. I am in very light polluted area, but I am fairly sure that the view of M13 is worse than through my old 130 Newtonian. Also struggling to bring single stars into sharp focus. Could this be an issue of collimation?

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I have recently purchase a celestron 6se and although I can see saturn fairly well (cannot see any banding or the cassini division), I am finding it almost impossible to make out any deep sky objects. I am in very light polluted area, but I am fairly sure that the view of M13 is worse than through my old 130 Newtonian. Also struggling to bring single stars into sharp focus. Could this be an issue of collimation?

Have you checked them side-by-side? Views of DSOs are very sensitive to LP and transparency of the sky. Not seeing the Cassini division is not too surprising, the rings are not really open, but banding should be apparent. Checking collimation is a good idea.

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I don't have my newtonian to hand unfortunately. Last night I tried numerous Mxxx objects and M13 was the only one I could begin to see. Definitely cannot see banding. I will hopefully check tonight. Little worried about playing about with collimation myself.

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I don't have my newtonian to hand unfortunately. Last night I tried numerous Mxxx objects and M13 was the only one I could begin to see. Definitely cannot see banding. I will hopefully check tonight. Little worried about playing about with collimation myself.

Getting the banding on Saturn can be a problem at low magnification due to the small size of the planetary image, and potential glare at that surface brightness. I tend to get it fairly easily at 93x, but more easily at 140x and higher in my C8.

It is not as difficult as people think to collimate a scope, don't worry too much.

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collimation of an sct is imo is easier than a newt but bobs knobs would be a good investment for it not having to twiddle about in the dark with a tool near my corrector plate makes collimating more comfortable

Edited by rowan46
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This may come in handy when doing a star test Diffraction pattern and aberrations

Also how long are you letting the scope cool down for as a SCT will take a lot longer than a 130p as this will effect performance.

SPACEBOY

This is possibly the source of the problem. Pretty much start observing as soon as the scope is outside.

How long does it need to cool for?

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I'm no expert but given it's size and closed tube design I'd estimate at least 1 1/2 - 3 hrs coming from a warm house and 40 mins - 1 1/2 hrs from a cool cellar or shaded out building. SCT owner may better advise you than I can but I can say you will be surprised at the difference it can make having the scope cooled to an ambient temperature. But be aware this is when dew is more likely to form over the corrector plate and dew shields / heaters are required.

Edited by spaceboy
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This is possibly the source of the problem. Pretty much start observing as soon as the scope is outside.

How long does it need to cool for?

i would say about an hour ideally, minimum 30 minutes. the air inside the scope will be warmer than the outside air, so you will want to remove any obstructions from the focuser and leave that end pointed upwards to let the air escape quicker, and get the scope to cool down nice and quick.

Edited by banner001
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i would say about an hour ideally, minimum 30 minutes. the air inside the scope will be warmer than the outside air, so you will want to remove any obstructions from the focuser and leave that end pointed upwards to let the air escape quicker, and get the scope to cool down nice and quick.

NO!! This lets dust in!! I leave my SCT closed. Let it cool for about one hour (and my C8 cools down more slowly than the smaller C6). I store my scope in a garage which is only heated a little during winter (only just above freezing point). I often get decent results after 30 min at low magnification. It is easy to tell your scope has not cooled down: the out-of focus image shows currents in the tube easily. For hasty people special SCT coolers are available, but I have not used them.

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so you will want to remove any obstructions from the focuser and leave that end pointed upwards to let the air escape quicker, and get the scope to cool down nice and quick.

Although this makes the most sense as hot air rises you also want to take into consideration on the very unlucky off chance some thing was to fall in to the OTA your going to be in for fun times trying to get it back out again.

EDIT: Sorry really must type quicker.

Edited by spaceboy
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I agree with Michael, you need at least an hour outside. and colimating a SCT is very easy, compared to a newt.

Also depending where you are there has been some very high Sirrius Cloud the last few nights which will not help viewing.

To do colimtion....................Go to Arcturus..............and get it center in the EP.

use a High mag EP and wind the focoser out until a Ring appears where the star was(doughnut). If it is off center........rest your finger on the edge of the front of the OTA. (do not touch the glass) look through the EP you will see your finger. Move your finger round the rim until it is next to part of the doughnut that is narrowist......then adjust one of the 3 screws on the corrector plate that is opposite the Finger.. adjust it until the doughnut is center..............Job Done

Edited by valleyman
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I agree with Michael, you need at least an hour outside. and colimating a SCT is very easy, compared to a newt.

Also depending where you are there has been some very high Sirrius Cloud the last few nights which will not help viewing.

To do colimtion....................Go to Arcturus..............and get it center in the EP.

use a High mag EP and wind the focoser out until a Ring appears where the star was(doughnut). If it is off center........rest your finger on the edge of the front of the OTA. (do not touch the glass) look through the EP you will see your finger. Move your finger round the rim until it is next to part of the doughnut that is narrowist......then adjust one of the 3 screws on the corrector plate that is opposite the Finger.. adjust it until the doughnut is center..............Job Done

I am in Surrey, where the clouds appear to have become more-or-less resident.

Thanks for this, I will try tonight.

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Although this makes the most sense as hot air rises you also want to take into consideration on the very unlucky off chance some thing was to fall in to the OTA your going to be in for fun times trying to get it back out again.

EDIT: Sorry really must type quicker.

You could always fix a square of gauze over the end with a laccy band to stop bits falling in.

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You could always fix a square of gauze over the end with a laccy band to stop bits falling in.

Fine meshed gauze kills convection (needed for cooling) quite readily, coarse-meshed gauze lets dust in (quite apart from most gauze being a source of dust).

Just leave it closed, and have a bit of patience. In winter, I set up the scope while it is still light, or just before dinner, and then start observing after dinner (and doing the dishes). When I get really impatient, I have a first look with either the bins or the 80mm apo.

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NO!! This lets dust in!! I leave my SCT closed. Let it cool for about one hour (and my C8 cools down more slowly than the smaller C6). I store my scope in a garage which is only heated a little during winter (only just above freezing point). I often get decent results after 30 min at low magnification. It is easy to tell your scope has not cooled down: the out-of focus image shows currents in the tube easily. For hasty people special SCT coolers are available, but I have not used them.

only quoting 'turn left at orion' :)

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