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Adreneline

Sony A7 help & advice please

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Posted (edited)

Hi Everyone

I have acquired a first generation Sony A7 body (not the S or the R - not Mk II or Mk III); a 'deal of the day' from a well known online supplier and with Sony cash back it was all a bit of a bargain as a full frame camera for general photography, as well as potentially AP.

I've mounted the A7 on my WO-ZS71 and got the spacing correct and even managed a first image of M31: this is just 10 x 30s frames at ISO 1600 focused using the 'live view' in the Sony Viewer PC application. I had hoped to get more lights and use longer exposure times but clouds put paid to that idea!

1083165390_m31_sony_a7_dss_ABE_ABEHT.thumb.jpg.3b05077aec04e87f454e0cb8ac76ef12.jpg

I've used DSS to stack the lights; I have yet to take calibration frames. Is there anything I need to be aware of in creating bias, dark and flat frames?

I understand the Sony does not use a bayer matrix; if that is the case what settings should I use in DSS or PI or even APP? For the above I used the Generic RGGB.

Any help or advice based on experience of using an A7 would be very much appreciated.

If it turns out not to be a good way to go for AP it is not the end of the world; as a full frame camera it will see plenty of use for general photography.

Many thanks in anticipation.

Adrian

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Edited by Adreneline
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26 minutes ago, Adreneline said:

I understand the Sony does not use a bayer matrix;

Where did you get this info from? Btw if you used RGGB in DSS and it worked - it's bayer matrix :D

Best approach re calibration would be to take all frames for first few targets and just try which calibration method gives best results (possible combos that work would be: light + dark, flat + flat dark, light + dark, flat + bias, light + bias, flat + bias). If you can find any sort of automatic dark current management and noise reduction in camera - turn it off and let regular calibration deal with those things.

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Hi vlaiv,

20 minutes ago, vlaiv said:

Where did you get this info from?

 

20 minutes ago, vlaiv said:

it's bayer matrix

I was confused because I stumbled across a couple of websites that seemed to imply the Sony sensor did not employ a bayer matrix - hence my question. As you say RGGB seemed to work so I'll go with that for now.

Regarding calibration frames I'll set about acquiring some as per my Canon 70D and see how it goes with the Sony.

Many thanks for your helpful reply.

Adrian

Edited by Adreneline

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Hi there - that's a really good image - nice widefield too!

I don't have an A7 but I did start a year ago with an A6500 which is probably not dissimilar to the A7 except being an APS-C camera.

Firstly I would say you can definitely use this camera for astrophotography! If you look my Astrobin link in my signature, the photos from Andromeda and before are all with the Sony.

On calibration:

Flats: Need to be at the same ISO, same orientation and same focus as your lights - and it is crucial they are done on the same night as your lights. The idea of flats is to remove dust specs and other blemishes (as well as vignetting) from your imaging train from the lights - so if you change anything before taking the flats, you'll probably have a different dust configuration on your lens, etc and the flats won't match! I use an illuminated tracing pad for my flats, but also have used the white t-shirt in front of a white word document. As long as the histogram is about half way or slightly less, it works fine.

Darks and biases are straightforward - for darks, you need the same ISO IIRC but definitely the ambient temp to be similar to your lights...so ASAP after imaging. Focus is not important here, you can actually do this with the sensor cap alone - make sure the length of the darks are the same as the lights. And keep the camera in a bag or dark room to minimise light bleed.

Biases are super simple - cover the lens/scope or use a sensor cap. Go to the shortest exposure length possible (on mine was 1/4000) and take multiple shots. Temp is important here too.

I tended to aim for 25-30 of each type of calibration frame which worked well for my camera. Time consuming with the darks, but worth it.

You should be able to toss all those into DSS and come up with a nice image. PI's batch preprocessing script should also work too! It will definitely have a bayer matrix.

I paired the a6500 up with a cheap intervalometer and it worked really well...the limiting factor will be when eventually you want to move to computer based image acquisition - the Sonys don't play well with software due to lack of USB tethering support from Sony. I eventually moved to mono + filters, but you can definitely have great success with the A7, I'm sure!

If you get yours modded to be more receptive to Ha, that would be cool - that was one of the reasons I ultimately moved to another camera.

Hope this helps!

Edited by eshy76
Grammar
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On 10/01/2019 at 15:04, eshy76 said:

Hi there - that's a really good image - nice widefield too!

Hi! Thank you so much for your response to my request for advice and my apologies it has taken me so long to respond - I only just saw your response and I most certainly did not get the Notification flag to say you had responded way back on 10th January.

What with the weather and the moon I've not used the A7 again since the beginning of the month; I was hoping that next week, with essentially no moon we might be blessed with some clear skies and I would give it another go. I have been playing around with the Sony software but as you say remote control is not that straightforward - what a shame there is no 'BackYardSony' or something similar.

Thanks for all the advice with calibration frames; I was planning on taking some Bias and Darks this weekend in preparation for using the A7 over the next week or so on the ZS71. I've also had a friend print me a Bahtinov Mask for the ZS71 to use with the A7 although I think my focus is pretty well sorted using the Viewer software.

Unless I am mistaken there is no way to connect an Intervalometer to the A7 - not that I can see.

I've also treated myself to a Samyang 22mm f2.4 lens so I might have a play at some seriously widefield if I can find a suitably dark site that's not a million miles away!

Thanks again and please accept my apologies for the tardy response.

Adrian

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Hi there - no problem at all. I would say that I did manage to connect an intervalometer to the A6500 - through the micro-USB port on the side. I think it was an S2 connection? This is the one I bought and it mentions the A7 in the description...do you have the micro-USB port? 

Neewer® LCD Digital Timer Remote Shutter Release Control Cable Cord Intervalometer Time-lapse Photography Device Compatible with RM-VPR1 Multi-Terminal Plug for SONY Alpha A7r, A7, A6000, A3000, SLT-A58, NEX-3NL, DSC-HX300, DSC-RX100M3, DSC-RX100M2, DSC-RX100III, DSC-RX100II Cameras

 

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