Over Exposed

[daryl_lincoln]

I have now managed after a long time to guide for 15mins

So now my question is, is it possible to over expose a image. I use a Meade DSI-II. Do i now need to play about with the gain and offset setting (which i never have done before as it complicated).

Or do i stick to short subs and lots of them but will this give me loss of detail?

[Catanonia]

I would say yes depending how much Light Pollution you have.

Before I got my LP clip filter 10 mins was max before blow out.

[roundycat]

the potential to guide for a long time is one of the most over rated things in astrophotography. An image taken with any camera can be over exposed, the time taken to do it varies according to lots of different things.

In astro work it is generally accepted that exposure time should be determined by the amount by which the sky background makes itself obvious. If you are getting a strong signal in the background for whatever reason you should limit it by the exposure time so it does not swamp the interesting bits. Typically, with a 16 bit range of adu something like 3000 adu would be plenty for an area with no interest, ie, the background.

Before you get to this point you may be lmited by other factors such as star bloat, blooming or guiding errors. Long sub exposures does not represent some sort of holy grail. The longer the subs the more difficult it is to eradicate such things as sat trails which generally need at least eight to ten subs.

I rarely go for longer than 15m and that would be exceptional in spite of the fact I can guide for an hour or more with no problems.

Dennis

[daryl_lincoln]

Ok understand a bit more now

Next question then what should the histogram look like on the read out

[roundycat]

I don't use a camera with a histogram readout like a DSLR so the only answer I can give is to show these two from Maxim screen grabs. These are both individual subs that went towards making acceptable finished pictures. Note the value of the adu counts.

Dennis