8 replies to this topic

[A_alharbi97]

Hello folks 

I’m facing a weird problem with my guide i was guiding using OAG with zwo 120mm and out of the blue I got line-shaped stars (attached) I thought it was from the prism i thought it was too high i managed to lower it till there is no pulling down and still have the same problem 

my light train is 

 

qhy 268 > zwo EFW > zwo OAG-L > esato > reduce 0.7 > 11” edge HD 

 

Any idea? 
 

note* i tightened OAG prism screw

 

i lowered the prism to the end ( also the camera to end down) 

 

at the start of the night (Ha filter)  it went well and them turned into line i believe with OIII FILTER ( maybe the focus is affecting the process ( just came in my mind didn’t test it yet) and if so what to do? 
 

CS 

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[speedster]

Is PHD giving you an error message?  In the next image in the sequence, is this star an equal length streak along the same path?  In other words, does it continue moving off of the guide cam sensor?  Is it moving in the direction of the RA axis?

[A_alharbi97]

Is PHD giving you an error message?  In the next image in the sequence, is this star an equal length streak along the same path?  In other words, does it continue moving off of the guide cam sensor?  Is it moving in the direction of the RA axis?

Nope it is still with no error message in fact my images are pretty good so i believe there’s nothing wrong with tracking it self, im using HAE 69 EC and shooting for 2.5 min subs images are fine but guiding stars line shape ( at this point i started shooting unguided) 

[cuzimthedad]

Moving to Beginning Deep Sky Observing...

[BucketDave]

I had funny shaped stars with my zwo OAG. It was caused by grazing incidence reflections off the wall of the tunnel, between the prism and the sensor. When a bright star was in just the right place, i could see a line through the star having the same shape as one half of the tunnel. Hence, people describing 'seagull shaped stars' in their OAG.

[KNak]

Yes exactly as BucketDave says.  Same thing on my Player One OAG, inner aperture of stalk is too reflective.  Shine a laser off something shiny onto a wall in your house and you'll see the same thing.  Not much to do about it, kinda shabby, but PHD will ignore if you set an appropriate max HFD

[michael8554]

Hi CS

 

Your OAG needs setting up correctly, you can't just lower the prism and expect it to work.

 

The prism needs to be adjacent to the long side of the QHY268.

 

Then lower the prism until its shadow shows on a Flat exposure.

 

Back off until Flats are clear of shadow.

 

Having said that, I don't believe a ZWO 120mm is sensitive enough for OAG purposes,  you may struggle to find guide stars.

[archiebald]

Yes exactly as BucketDave says.  Same thing on my Player One OAG, inner aperture of stalk is too reflective.  Shine a laser off something shiny onto a wall in your house and you'll see the same thing.  Not much to do about it, kinda shabby, but PHD will ignore if you set an appropriate max HFD

Up to now I've never seen this with my Player One OAG.

I just installed a Xena-M which has virtually 100% coverage of the prism - very well shaped stars in all locations both with my Z73 and Askar 120.

 

 

Hi CS

 

Your OAG needs setting up correctly, you can't just lower the prism and expect it to work.

 

The prism needs to be adjacent to the long side of the QHY268.

 

Then lower the prism until its shadow shows on a Flat exposure.

 

Back off until Flats are clear of shadow.

 

Having said that, I don't believe a ZWO 120mm is sensitive enough for OAG purposes,  you may struggle to find guide stars.

Agree with this, I'm using much less focal length, but I also found the ASI120mm to be very poor with an OAG (it's fine for a guide scope).  I instantly got much better and more consistent performance after recently changing to the Player One Xena-M (IMX249 sensor) - better sensitivity and a larger sensor

[KNak]

Up to now I've never seen this with my Player One OAG.

 

Could be I have a lemon but I gather they're all

machined the same. Not every frame, but when it occurs it 100% correlates with bright stars just outside the guider FOV.  Player One's response was effectively "this is normal"