Tracking Question

[biondi]

Hi All,

I have a C8 with a HEQ5 Pro and am just trying to play around with AP using a Dynax 5D dslr. I know this dslr isn't perhaps best suited but once I can master the basics I may replace it.

My question is regarding tracking. After Polar Aligning and then using a 3-star alignment it's fine for visual observing. However, when I tried taking a 300sec exposure the tracking was obviously out in the resulting raw image. So, how do others align before exposing is I guess my question? I don't have a guide scope, I wasn't going to invest in one of these unless I get a bit more 'into it'.

cheers all!

Matt

[Capricorn]

300sec isn't going to be possible without guiding, even then it is a bit extreme.

For "long" exposures the alignment has to be very accurate, the "standard" visual alignment set up is nowhere near accurate enough.

Drift aligning is an option for better accuracy, suspect that it takes several times longer to accomplish. Say an hour (utter guesswork)

Then I would say that if done well you might get 30-60 second exposures.

The idea is not to get one long exposure but several shortish ones then stack them, try ten 30 second exposures not one 300 sec exposure, then stack one on top of the other.

Isn't the C8 an SCT?

If so then being a long focal length the alignment will have to be VERY accurate without guidance.

[biondi]

Hi Capricorn,

Many thaks for responding, I'll take a look into drift alignment. You're right, it is an SCT - I have been looking at a focal reducer to take it down to f6.3 (from f10) which would help. That's a good point actually. I just didn't fancy spending out the £200 approx to buy one just yet

Thanks,

Matt

[Pete Presland]

it will take some very good alignment or guiding to use for dso's, have you tried using it for planets ? it would be excellent with a webcam in it

[Capricorn]

Matt, Astrophotography is a bad area, and tends to go against the "standadrd" thinking.

The people that are really into it can be using RC scopes that cost several thousands, most it would seem stick to the short apo refractors not even the larger apo refractors. Ones in the area of 80mm and f/5 - f/6 being the general.

In most of this hobby the cry of more aperture seems to rule.

Then comes the actual focal length, the longer that is then the more tracking errors become apparent, so the "preference" is for short focal length scopes. It is actually a double whammy, the longer focal length means keeping the image stable is a greater problem and the longer focal length means a bigger but dimmer image so longer exposures are needed.

I recall about 15-18 months ago one SGL'r saying thay had spent some £15,000 on their imaging kit so far, and that another £5,000 might get them to the kit they wanted.

Best not discuss mounts, they are really expensive and really big. An imager will put an 80mm refractor on an EQ6 and hope it will be OK. Someone thinking of getting into astronomy+AP wil think of a 200P and ask if an EQ3 is OK.

Cameras: people jump at sticking a DSLR on, say 18Mp if possible (back to bigger is better right ??). Imagers will often use a 2Mp ccd. Smaller chip and a lot less pixels.

As I said AP tends to go against what is often the normal in this.

[pilkinn]

Hi Matt. The C8 is ideal for planetary imaging and you don't need to guide. You will need to get a camera that can take videos at high frame rates. A webcam is fine to start with. For DSOs guiding is a must especially at the focal length of a C8 (even with the focal reducer).

Sent from my HTC Desire S using Tapatalk 2

[biondi]

Capricorn / Pilkinn - thanks very much for responding. Points taken..

Matt