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After a frustrating Monday night where everything went wrong, I managed a hassle free night last night. Polar alignment was better, laptop was connected and focus was as good as I could get with the coarse focus on my C8 SCT and BYEOS. 15 x 90s Lights @ISO800, 20 darks, 20 bais and 20 flats.

I could not get DSS to stack the images. After doing a bit of reading I think it was because my focus and alignment weren't perfect. I manged to get them stacked in Sequator but as far as I can tell it only uses darks and flats.

Anywho, with a little tickling in Gimp, this is what I ended up with.

One question, when you see the images with the pink nebula stretching off in all directions, is this created by longer exposures or is that a narrow band filter?

M42_GIMP_1_JPEG.jpg

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This is one of the few objects that responds well to different exposure lengths. As you can see, your 90s subs are already burning out the center of the nebula. So it might be worth taking some shorter subs (say 20s) to bring out the center of the nebula. Longer exposures (or, more precisely, a longer integrated time) will show fainter material and spread the nebula (subject to fogging by LP). Modding your canon, so that it sees more in the red band, will also cause you to see more of the nebula. A Ha filter will mean that you don't see so much of anything else and so make the nebula more "contrasty" and show more detail.

You can get clip in filters for your canon, but I would suggest getting an Ha filter for an unmodded canon would be a bit of a waste.

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Thank you @Demonperformer. I was thinking of trying shorter subs next time as I was clearly having issues with alignment and focus. I guess starting out with an f10 scope isn't ideal either.

Does anyone have any suggestions regarding focus? The C8 has the standard focus adjuster assembly and I simply watched the FWHM readout in BYEOS. I found there was a dead spot where I could change the focus slightly and the FWHM wouldn't change. I assume this was due to the fact that it was about as good as it was going to get. Is the bast way to get to that point and then start taking sample shots?

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Not a cheap option, but I found focussing on the 8se became much easier when I added a microfocusser. A similar result is sometimes obtained by adding a bigger circumference wheel to the standard focusser. It may be worth checking your collimation if you are having problems with focus.

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I had planned on getting the feather touch micro focusser from Starlight Instruments but as you say, they're pricey. I was watching a video on how to install them and noticed I can pull the rubber knob off the focus shaft! I will turn down a bit of aluminium at work to aid focus until I can afford the proper kit!

Collimation had been mentioned by someone else too. Unfortunately, I forgot to check it. Plan to simply look at a bright star out of focus and aim for concentric rings.

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2 hours ago, hornedreaper33 said:

I had planned on getting the feather touch micro focusser from Starlight Instruments but as you say, they're pricey. I was watching a video on how to install them and noticed I can pull the rubber knob off the focus shaft! I will turn down a bit of aluminium at work to aid focus until I can afford the proper kit!

Collimation had been mentioned by someone else too. Unfortunately, I forgot to check it. Plan to simply look at a bright star out of focus and aim for concentric rings.

Take a look at the new Celestron motor Focuser, which is supported by CPWI software now being public beta tested in TeamCelestron. CPWI will replace Nexremote and SkyQLink and offer direct wireless connectivity to a Windows laptop without any messing about with cables attached to the HC or PL2303 drivers. You just need a SkyPortal dongle and CPWI. This will manage scope and focusser. 

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Interesting...

I can't seem to find any reviews/ experience with this new Celestron focuser - or any vendor offering them.

I used the Vegemite lid, larger knob option on the C9.25/ C11 for many years then adapted a SW motor as a belt drive...changed to the micro focuser on the C9.25 - absolutely great!

On the C11 I now use the JMI focus motor and the computer control. Works very well for me and meets my spectroscopic needs.

 

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Vegemite ... that was the word I couldn't remember!

9 hours ago, hornedreaper33 said:

Plan to simply look at a bright star out of focus and aim for concentric rings.

That's it. If you find yourself needing to collimate regularly, it can be worth investing in a set of Bobs Knobs - much easier than fiddling with an allen key in the dark near your precious front-plate.

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Thanks for the suggestions everyone. I had a look at the collimation last night, it was very slightly out. So very slightly that I could barely tell that it was off centre. I had a tweak of the screws and got it centred (as far as I could tell). Transparency was bad and the telescope was pretty warm so I'll have to check it again when we have some clear skies.

As it's Friday and I have a workshop at my disposal, I think I will be making a large focus knob today. Probably knock together some of bob's knobs when I get the chance as that seems like a great upgrade. I'll avoid it for now as it requires completely screwing (ha!) the collimation to replace the screws. 

I did however, order a Bahtinov mask. Hopefully with the big focus knob, the mask and the Bahtinov mask focus mode on BYEOS, I can get some pin sharp stars.

 

Thanks for all the suggestions!

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When focusing the American SCTs with the moving mirror system your last adjustment should always be anti-cloockwise. That's the direction which pushes the mirror up the tube. Turning the other way can leave the mirror not fully returned back down again so it shifts over time.

Olly

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