Guiding problems

[Carole]

(See my American Nebula)
I started guiding at the beginning of 2010 and had no problems with guiding until the last few images.

I decided to watch it last night to see what was actually happening and every so often it would lose the star, and then latch onto it again.  I had it set to 0.5 last night. 

Any ideas any-one?
I guess I should have watched the histogram, I haven't remembered to do that yet. 

Carole

[RobertM]

What did you have set to 0.5 ?

[MarkS]

In what way did PhD lose the star? 
Did the star "jump" outside the search rectangle? 
Or did the star's SNR drop too far?

[Carole]

What did you have set to 0.5 ?

The littledrop box centre bottom, I think this is the exposure.

Did the star "jump" outside the search rectangle? 
Or did the star's SNR drop too far?

It did jump outside the rectangle at one point near the beginning but I had the drop box set at 0.02 (it had defaulted to this), so I stopped and repositioned PHD and re-set drop box at 0.5. 
I think the rest of the time the SNR dropped too far and the green box round the star changed to orange until it latched onto it again. 

Should I set it to 1.0?

Carole

[RobertM]

0.5s is low andcould lead to too many guide corrections especially in bad seeing which could contribute to you loosing your guide star.  I generally use 3-5 second exposures at home to average seeing but I can use much shorter guide exposures at DSC because of the more stable conditions.

Robert

[Carole]

Thanks Robert, I will use longer exposure in PHD.  It might well be I had a longer setting at one time and some-how it got changed and I didn't remember what the best setting should have been.

One day I'll actually do an image with everything right!!!  Focus, guiding.
At least I got the focus right on the NA Nebula as I got it really accurate in Bahtinov grabber.  

Two steps forward and 1 1/2 steps back every time!!!!

Carole

[MarkS]

One day I'll actually do an image with everything right!!!  Focus, guiding.
At least I got the focus right on the NA Nebula as I got it really accurate in Bahtinov grabber. 

Two steps forward and 1 1/2 steps back every time!!!!

Carole,

Part of the reason for this is that you are trying to learn everything at once and so there are lots of things unfamiliar to you in your imaging setup, any one of which might go wrong.  You have jumped straight into the full complexity of guided imaging whereas most people take a more step by step approach.  In my own case I was regularly imaging for 15 months before I began to use a laptop PC or even attempt guiding.  But I gained confidence in using my camera on my scope and during that time I produced many images I am still very proud of. 

If I'm honest, I think your approach is more likely to lead to frustration because with so many things to go wrong, one of them will go wrong and the chance of getting a successful image on a particular evening is much smaller.   It was the continuing pleasure of producing good images that drove me forwards to improve my technique and to add useful extra bits of equipment as required.

Having said that, I think you are almost there now and you will be producing fine images like the rest of us.  But I don't envy the path you have taken.

Mark

[Carole]

I am surprised to hear that Mark, as I thought I was being very slow at getting to grips with everything. 

I am enjoying the challenge though despite its frustrations, just sorry I have to keep asking questions but I don't have enough technical understanding to know when and why things go wrong.

Carole

[RobertM]

I agree with Mark, starting off can be very daunting, especially if you start off near the deep end.

As you're now starting to find out that everything is critical it might be worthwhile putting together a checklist while you're still learning the in's and out's... just a thought.

Robert

[Carole]

it might be worthwhile putting together a checklist

I have got a file of information, and also have a set up "routine". 

But as I have occasionally forgotten something it might be a good idea (like forgetting to put the splitters on so I could use my dew heaters), but as it is all set up in the Observatory it's only really when I go to DSC that the routine goes awry.

I do need to make a list of things like default and normal settings though.

Carole

[mickw]

it's only really when I go to DSC that the routine goes awry

Carole, you imaged NA in the observatory and forgot the Bias Frames.

This was not me taking the P, but how hard is to make a list and use it until it becomes second nature ?  Stick one in the car and one in the observatory - sorted

Unfortunately I've actually got to do something so I can make a list of what I did

[Rocket Pooch]

Clouds?

[Mac]

Clouds?

You could order this as a starter.

http://www.transair.co.uk/product4.asp?SID=2&Product_ID=1070

I agree with Robert.

Make yourself a complete check list.

Starting from

Erect Tripod
Point North
Level Tripod
Mount telescopes
Add camera ect, ect,
Check level again
Polar align

ect, ect

Main camera in usb1
guide in usb2

ect, ect.

You might think is silly to put things down line point north, or level tripod,

but after you have set everything up, its a bugger to try and remember did i do that or not.
and if you are not north, level and polar aligned, then this is just going to add to your problems
as you will believe these have been done and its the guiding thats against you.

Ask Fay, I believe she has polar aligned on the wrong star, as have I. And that really does make you scratch your head.

Mac.

[Carole]

Clouds?

I am 99% sure the clouds came later Chris, unless maybe there was a thin layer I wasn't aware of, but this has been a problem the last 2 or 3 times I have imaged, so it has to be more than clouds.

Carole, you imaged NA in the observatory and forgot the Bias Frames.

I don't do BIAS frames every time Mick as I am building up a library of them same as I am with darks.  They just happened to be on a different PC when I did the processing and thought I'd get them later and in my enthusiasm forgot.  Also to be honest I hadn't realised how critical they were until now. Also I read this

You don't need to take new Bias frames very often, just once or twice a year, because the read noise doesn't change much over the life of a DSLR.

Main camera in usb1 guide in usb2

If these were not plugged in the same USB port, could that cause guide problems, the laptop recognised them when they were plugged in with a little beep and all cameras and mount were recognised?  

Carole

[Rocket Pooch]

Sounds like cables to me?