Phd noise issues

[Gaztronomer]

Hi all

I was out last night and was trying to picture andromeda

for guiding I use a 80mm celestron tube and an imaging source DFK 21AU04.AS camera along with PHD software, I could not for the life of me get any where near locking on to a guide star as I could not get any in focus over the amount of noise being displayed on screen.

i has so much noise and hiss that it was like a TV from the 1970's.

would this be the right camera to use as a guide camera or should I look at another model / type, or do you have any tips for sorting out PHD and noise reduction.

any help would be great.

thanks

gaz

[Mike_F]

Too much noise sometimes can be a symptom of an exposure time that's too short.

I normally use an exposure in the 1 to 5 seconds range when guiding with my Lodestar - depending on how bright the guide star is I've chosen. How long an exposure are you using?

[cfpendock]

As Mike_F says, exposure times need to be more or less correct - try playing with the gain and exposure time controls. Also, I have found PHD can show only noise if there is no reasonably clearly defined star. Sometimes I have used the IC capture programme (shipped with the camera) to set up focus and exposure. Then I switch over to PHD and normally it works.

Chris

[r3i]

I've seen reports of others successfully using this camera as a guide camera. I would agree with Mike_F that it does sound like your exposure time is too short and you want to be setting it to be in the range he specified.

[cp255]

There are two things you can do which in my opinion work better than increasing the exposure length. First turn on noise reduction which can be found by clicking on the brain menu. I think one is a median and the other is an average. Choose either one. Next there is an option to take dark frames on the home screen. Click that button and follow the instructions. I usually use 0.5 sec exposures and I get decent SNR using these steps.

[Ant]

As Mike_F says, exposure times need to be more or less correct - try playing with the gain and exposure time controls. Also, I have found PHD can show only noise if there is no reasonably clearly defined star. Sometimes I have used the IC capture programme (shipped with the camera) to set up focus and exposure. Then I switch over to PHD and normally it works.

Chris

I couldn't agree with this more. If there is no guide star present, or it is out of focus enough there is an abundance of noise, as soon as the war comes onto the screen or in focus all the noise goes aware.

i have taken to measuring the amount of draw tube showing so that I am close to being in focus before I even start capturing... Works for me.

Ant

[Freddie]

Before I got my DMK I used my DBK with an ST80 no problems. As CP255 says, taking darks is helpful but I really don't think that 0.5 sec exposures are a good idea as this is too fast for typical seeing so isn't going to be good for your guiding. Something like 2.5 sec on PHD and 2.8 sec on the cam is what I typically use.

[Gaztronomer]

Many thanks

im glad to see that it's only a setting issue and not more hardware needed, I had another go toningt and changed a few things and it seem loads better.

would a tru guide scope camera make a difference something like the orion stars shoot or the loadstar

many thanks

[Daniel-K]

i use a qhy5 and have no issues with a finder guider, 3 sec exposures callibration in 9 steps flat graphs does the job for me

[Mike_F]

I really don't think that 0.5 sec exposures are a good idea as this is too fast for typical seeing so isn't going to be good for your guiding. Something like 2.5 sec on PHD and 2.8 sec on the cam is what I typically use.

Totally agree with this. Received wisdom is that a guide exposure of less than one second is going to result in you "chasing the seeing" - i.e. seeing conditions will mess with PHD's sub-pixel calculations of where the star's centroid is.

would a tru guide scope camera make a difference something like the orion stars shoot or the loadstar

Initially, I wasn't going to comment on your camera because I have no experience with the Imaging Source cameras (yet); but since you asked the question I went and looked up the specs. If I'm reading your model number correctly - that seems to be a colour camera? If that's the case, then a dedicated mono guide cam is definitely a better choice.

Here's the relevant extract from what I consider to be the PHD "bible" : http://www.rosecitya...deToGuiding.pdf

(Page 13): "Because sensitivity and low noise are important to guiding, a color camera should pretty

much never be used. The color filters substantially reduce the amount of light that reaches

the sensor. Furthermore, differences in brightness between red, green and blue filters will

cause errors in calculating the location of the guide star's centroid."

If you're after recommendations, I've only got experience with a QHY5v and the Lodestar. The QHY5v is a great little budget cam and works well as a guider, but I found mine a little "noisy".

Since moving to OAG, I've needed something a little more sensitive and quiet, and the Lodestar perfectly fits that bill. But, that sensitivity and silence comes at a commensurately higher price, and it's cabling arrangement is, ermm.. "sub optimal".

You pays your money.. (etc.)

Hope that helps.

[Ant]

Oh but the lodestar is an AMAZING camera, the first I used it I nearly wet myself.

I never got my QHY5 to work properly, i had to use the DMK as a guide cam as this was what I had. I didn't have anything else and they do work and so does the DBK - they are just not ideal But if that's what you have that's what you use.

When using the DMK21(mono) through the OAG, I was used to seeing at least one star to choose - usually there were two in any given FOV. The first attempt with the Lodestar showed me a screen with literally 30 stars to choose from. I really couldn't believe my luck.

It has completely transformed my guiding. I know it's more money - but it is REALLY worth it.

Cheers

Ant

p.s. Can you tell that I really like the Lodestar?

[Mike_F]

p.s. Can you tell that I really like the Lodestar?

Yes, me too, and at the risk of hijacking Gaztronomer's thread - the Loadstar sensitivity is indeed amazing. The irony that I saw my first ever galaxy in my guide cam's picture has not been lost on me. Just 1 sec exposure is enough for it to show the core of M81 very clearly indeed.

I just object to having to pay 35 quid for a piece of plastic to fix the lack of strain relief on what should be a very simple thing for SX to fix - on a camera that cost me the thick end of 400 notes.

[Gaztronomer]

Hi

again thanks for all the info it's a great help.

is there any particular loadstar model that I should look at or is there only one

Thanks

[Gaztronomer]

Hi

again thanks for all the info it's a great help.

is there any particular loadstar model that I should look at or is there only one, or is the better option an orion starshoot.

Thanks