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iwols

oag quality and camera sensitivity

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Posted (edited)

hi all after problems with my oag just thought i would start a new topic,is there a difference in the quality of oag(ie do some let more star light through to the camera) and what is a good sensitive camera to use (better than a qhy5 ii) i need some advice desperately

Edited by iwols

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What seems to be the problem with OAG?

I suspect most OAGs will be about the same - prism quality wise. Main differences will be mechanical.

Most cameras, including QHY5II, will be sensitive enough.

What can make difference is prism positioning. It will depend on F/ratio of the scope. Prisms can vignette on fast scopes and can act as if stopped down if they are moved further away.

Let's say you have 8mm prism and you put your prism so that prism / guide sensor is at 80mm. You will effectively work your OAG on F/10. If you have faster scope, you'll benefit from moving prism closer to imaging sensor (and hence focal plane).

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Posted (edited)

well had trouble in phd,so decided to start again and removed blade holding prism out and the prism fell off replaced but struggling to get a good snr in phd see seperate topic cheers  

 

Edited by iwols

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Here are couple of questions that might help:

1. Any chance you have filters in front of OAG? (those should be between OAG and imaging sensor - light for OAG should be unfiltered)

2. What is OAG / imaging sensor distance?

3. What is your guide exposure? Have you tried PHD2? Maybe it will work better than PHD.

4. What drivers are you using for QHY5II? Switching to ASCOM instead of native helps with SNR (fact that it will read 12bit values instead of 8bit). What sort of gain are you using with this camera?

5. What is focus of your OAG like? Do you have sharply defined stars in PHD or are they smeared out?

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All ok but where in phd2 do i adjust gain please

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12 minutes ago, iwols said:

where in phd2 do i adjust gain please

2106245764_Screenshotfrom2019-04-2114-06-51.png.2dbf0852e4676dd4bab9eb8089e8b2f5.png

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thanks alicante what ver are you using

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In what way is low snr affecting your guiding ?

Is PHD2 failing to autoselect a star ?

Or are you getting Star Lost messages ?

Michael 

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Maybe your PHD2 settings are causing the message when in fact there are stars available.

Are you using Star Mass Detection in the Guiding tab?

You could try Minimum star HFD (pixels) instead on the same screen.

Set to 2 pixels so it doesn't select a hot pixel.

Also what camera exposure are you using?

Michael 

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Posted (edited)
11 hours ago, iwols said:

what ver are you using

2.6.6 via t7m and canon oag; tested up to 1600mm focal length.

HTH

Edited by alacant
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thanks but same here 2.6.6 but i have no option

 

 

 

Screenshot 2019-04-21 21.26.54.png

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34 minutes ago, iwols said:

i have no option

Use the QHY ASCOM driver.

Cheers

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