Full disc solar cam

[mason]

Hi there,

I have a Lunt 35 h-alpha scope and would like to take full disc images.

Can someone advise me on what mono camera would be best for this. What chip size would be best? I have been looking at the QHY5 11 Mono cam with the large chip size. Has anyone had much experience with this cam, as it seems quite cheap.

Thanks.

Mason.

[DrRobin]

Hi,

I think some people have reported 'newton rings' with a QHY5 II.  The sun will have an angular size of about 31' (Arc minutes) and given your scope (400mm fl) the sun will fit in a 1/2" sensor with no barlow or reducer.  The QHY5-II and DMK41 are both 1/2" sensors.  A lot of solar imagers use the DMK41, but they are not cheap and there are other cameras like the Point Grey Chameleon now also been used.

Robin

[mason]

Thanks for the reply. How about the QHY5L 11 with the 1/3 chip? 

[JamesF]

As Robin says, the Sun is around 31 arcminutes across.  It varies depending on the time of year and around now when we're closest to it it will actually be nearer 32.7 arcminutes.  At a 400mm focal length you will get about 8.6 arcminutes per mm at the image plane, so the smallest dimension of the sensor chip must be at least 3.8mm.  The QHY5L-II sensor is only 3.63mm on the shortest side, so you're never going to get it in a single hit.  Mosaics will be required.  My ASI120MM has the same chip and with my PST (also 400mm focal length) the image won't fit on the sensor in one go.

The MT9M034 sensor in both these cameras may also produce newton's rings in the image, though I've read that if the camera is tilted fractionally the problem can be mitigated.  I think I can see them sometimes with mine, but not always.

The DMK41 is regularly used for solar imaging as it has a much larger sensor.  Sadly it has a price tag to match

It strikes me that actually the QHY5L-II might be quite handy for solar imaging with the PST if it doesn't produce images with artefacts because it can be put all the way down inside the eyepiece holder, potentially avoiding the issues with backfocus that most cameras have.

James

[DrRobin]

Hi,

For solar Ha you need a mono camera not a colour camera.  Ha is narrow band, only in the red spectrum and using a colour camera you will throw away 2/3rds of the image for a start, but the intense red will bleed over to the blue and green channels and create a fuzzy or soft focus image.

The QHY5-II in mono is 1/2", but the colour is 1/3".  A 1/3" chip will not give you a full disc on your Lunt 35. 

I am guessing you are trying to save a bit of money and buy one camera for the planets and solar Ha?  Unfortunately, it won't work, you will have to have a mono camera for Ha.  You could buy a filter wheel and filters and image the planets in colour, it will give you better images but is more effort.

If you want to check field of view of any set up go to http://starizona.com/acb/ccd/calc_pixel.aspx

Robin

Robin

[DrRobin]

Ah James beat me to some of the points.

The QHY5-II in mono is a 1/2" chip, here are the specs.

APTIMA CMOS Sensor MT9M001
Format: 1/2 inch, 6.66mm x 5.32mm
Pixel Size: 5.2um x 5.2um (1280 x 1024) 1.3 Mega Pixels
30fps @ 1280 x 1024 to 170fps @ 400 x 400

If there are no artifacts, it would probably be good, a lot cheaper than a DMK41.  Sadly I bought a QHY5 (old style) a couple of months before the new one came out for a night time guide cam, otherwise, I would have had a go with a QHY5-II for solar by now.

Robin

[JamesF]

QHY seem to use very confusing model names for their cameras

My understanding is that the QHY5-II (mono only) is 1/2" and both the QHY5L-II colour and mono are 1/3".  The latter may suffer from newton's rings.  I've heard it said and sometimes I believe I can see them in my own solar images using the same sensor, albeit in a different camera.  I have no experience with the QHY5-II, but if Robin says it also suffers from newton's rings I wouldn't doubt it.  I believe the rings are an artefact caused by light reflecting off the cover glass on the sensor resulting in interference, so it's most likely to be the same in all cameras with the same sensor.

Unlike the ASI120MM, slightly tilting the camera may be hard to make work with the QHY5L-II due to the way it fits.

James

[DrRobin]

There is a DMK41 on ABS for £225, looks a good deal to me.

I hadn't spotted the QHY5L is also available in mono, I had thought it was just colour, but I see it is both.

Robin

[mason]

Thanks for all your advice guys.

I have an imaging source 21au618 mono cam for planetary through a c9.25. I also have a lunt LS35.

I realise i need a mono cam for H alpha work, but the au612 requires alot of mosaics for full disc. Maybe im a bit lazy and just want no nonsense when i comes to solar work.

I also have a skywatcher 80 ed pro, which i use for lunar, and would also like to do full disc images on this too. I think in conclusion, the DMK41 is the cam to go for. I will have a look at the one on ABS. 

Thanks again.

[mason]

Ps, i cant work out what ABS stands for, thought it was astro boot sale! Can someone enlighten me 

[mason]

Astro buy and sell !!!! sussed it.

[DrRobin]

Sorry, should have done this in the first place.

http://www.astrobuysell.com/uk/propview.php?view=75132

Hope you get it.

Robin

[mason]

Thanks, have sent an e mail. My fingers are crossed. Many thanks for letting me know.