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Small DSLR or digital camera for use with 8” hyperstar or TASA

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#1 jprideaux

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Posted 21 March 2019 - 06:33 AM

Although there had been a bit of discussion in other forums about which dedicated astro-camera to use with a hyperstar or Rasa telescope with 8” aperture, I cannot find recommendations for DSLR or other (like mirrowless) recommendations. One important consideration would be that the body would need to be very small - ideally the longest dimension 4” or less. Anybody using anything like this? I am in the market for a new general- purpose camera and figured it might be nice to get one that could also be used for a hyperstar or Rasa (should I decide to get one of those).

#2 Ian Robinson

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Posted 21 March 2019 - 07:14 AM

I think it comes down to how large an obstruction you can tolerate at the front of the Hyperstar or RASA 8" SCT.

There are some very nice APS-C point and shoot cameras about, maybe one of these can modded (lens removed and IR filter removed to do the job).

Edited by Ian Robinson, 21 March 2019 - 07:17 AM.


#3 james7ca

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Posted 21 March 2019 - 07:29 AM

I think the old Sony NEX-5N and 5R were both very good mirrorless, APS-C cameras for astrophotography. Unfortunately, they stopped being made a few years ago and have been replaced by the Sony Alpha series which could be worse for astrophotography given the well-known star eater problem that I think Sony introduced sometime after the 5N and 5R.

 

The NEX-5N and 5R used Sony's IMX071 sensor which is also used in some of ZWO's and QHY's dedicated astro cameras. The only real problem with either of these NEX cameras is that they didn't have a built-in intervalometer for timed sequences and I think that today the only solution you are going to find to add that capability is to make your own IR-dongle which can then be controlled with a time lapse or remote shutter app on a smart phone, tablet, or iPod touch.

 

Both of the NEX cameras also had a first-curtain electronic shutter mode, which is very useful to reduce shutter slap and vibration and it also cuts down on the number of activations of the mechanical focal plane shutter (which has a limited life, maybe a few hundred thousand activations which can go pretty quick if you are taking a thousand or more images per night -- six hours of 30 second exposures is 720 subs, then add darks and bias files are you are up to near a thousand shots per night).

 

In any case, if you are looking for a mirrorless camera for a Hyperstar or RASA then you should definitely look for a device that has a built-in intervalometer and a first-curtain electronic shutter mode (IMO). Also, many or the newer cameras have done away with the IR remote capability, replacing that with WiFi which can be problematic as well as a real battery hog. Unfortunately, I don't think there is any camera on the market today that meets all of the above requirements.

 

Another camera that might be a candidate is the Panasonic model that uses the same sensor as found in ZWO's ASI1600 camera (and the similar model from QHY). The Panasonic Lumix G7 uses this sensor (as do some of the G7's siblings). Unfortunately, the Panasonic cameras don't support the first-curtain electronic shutter control for exposures over a certain limit (any exposure longer than one second, so too short to be useful for most astrophotography).

 

Then there is the issue of camera control and the only brands that have decent support within astrophotography applications are from Canon and Nikon (AFAIK, but that may have changed in the last year or two). So, combine that requirement (Canon or Nikon) with the need for a good sensor and with the desire (but not a requirement) for a built-in intervalometer and a first-curtain electronic shutter option and you MAY come up empty handed.

 

[UPDATE]

Cleared up some potentially misleading information about electronic shutters (should be called first-curtain electronic shutter rather than a fully electronic shutter, the latter would require a so-called global shutter which I don't think can be gotten in any current mirrorless, interchangeable lens camera).

[/UPDATE]


Edited by james7ca, 21 March 2019 - 11:43 AM.


#4 djdoud

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Posted 21 March 2019 - 07:33 AM

I've used a micro 4/3 camera (Zcam E1) on a RASA 8.

 Adapter Flange to Focal Plane distance on the RASA 8 is 25mm. With the flange to sensor distance on the micro 4/3 at 19.25 mm - no off the shelf adapter was thin enough to get the spacing correct. I had to modify an ebay sourced m 4/3 to T thread adapter on a lathe to get the right spacing. So spacing can be a challenge and something to consider when selecting a camera

On the plus side, the Zcam E1 is small and does not block the aperture at all. WIFI and battery power mean no cables across the corrector. Pixel  size is 3.8 um and a good match for the RASA 8.  I had one laying about but they do trade on ebay around 200 USD (E1 is no longer in production)  . I used folder monitor camera feature in sharpcap to live stack it. The lack of an off the shelf adapter and being OOP makes It a DIY kind of camera. I've switched to an ASI1600MC for native support in Sharpcap. So astro software support for camera is a consideration too.

Loving the RASA 8 with either camera


Edited by djdoud, 21 March 2019 - 07:37 AM.


#5 james7ca

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Posted 21 March 2019 - 07:36 AM

I think it comes down to how large an obstruction you can tolerate at the front of the Hyperstar or RASA 8" SCT.

There are some very nice APS-C point and shoot cameras about, maybe one of these can modded (lens removed and IR filter removed to do the job).

Many point and shoot cameras use a between-the-lens shutter. So, if you remove the lens you have no way to control the exposure. So, you either need a camera that has a fully electronic shutter or one that has a focal plane shutter (the latter standard on most -- all? -- removable lens cameras).


Edited by james7ca, 21 March 2019 - 11:29 AM.


#6 Ian Robinson

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Posted 21 March 2019 - 08:53 AM

I think the old Sony NEX-5N and 5R were both very good mirrorless, APS-C cameras for astrophotography. Unfortunately, they stopped being made a few years ago and have been replaced by the Sony Alpha series which could be worse for astrophotography given the well-known star eater problem that I think Sony introduced sometime after the 5N and 5R.
 
The NEX-5N and 5R used Sony's IMX071 sensor which is also used in ZWO's and QHY's dedicated astro cameras. The only real problem with either of these cameras is that they didn't have a built-in intervalometer for timed sequences and I think that today the only solution you are going to find to add that capability is to make your own IR-dongle and attach that to the audio headphone port on a smart phone or tablet or iPod touch and then control the camera using an app on said phone, tablet, or iPod touch. Both of these cameras also had a fully electronic shutter mode, which is very useful to prevent shutter slap and vibration and  it also cuts down on the number of activations of the mechanical focal plane shutter (which has a limited life, maybe a few hundred thousand activations which can go pretty quick if you are taking a thousand or more images per night -- six hours of 30 second exposures is 720 subs, then add darks and bias files are you are up to near a thousand shots per night).
 
In any case, if you are looking for a mirrorless camera for a Hyperstar or RASA then you should definitely look for a device that has a built-in intervalometer and a fully electronic shutter mode (IMO). Unfortunately, as far as I know there is no product like that on the market today. Also, many or the newer cameras have done away with the IR remote capability, replacing that with WiFi which can be problematic as well as a real battery hog.
 
Another camera that might be a candidate is the Panasonic model that uses the same sensor as found in ZWO's ASI1600 camera. Unfortunately, that camera doesn't support fully-electronic shutter control for exposures over a certain limit (something like any exposure longer than one second, not sure, but too short to be useful for most astrophotography).
 
Then there is the issue of camera control and the only brands that have decent support within astrophotography applications are from Canon and Nikon (AFAIK, but that may have changed in the last year or two). So, combine that requirement (Canon or Nikon) with the need for a good sensor and with the desire (but not a requirement) for a built-in intervalometer and a fully electronic shutter and you MAY come up empty handed.


Maybe someone might do a camera control software hack to fix that shortcoming.

#7 randcpoll

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Posted 21 March 2019 - 09:31 AM

A nice thing about Canon is that they have plenty of support software.

 

The smallest Canon DSLR that also has a nice APS-sized sensor is the SL2.

 

That will block the front of your OTA with dimensions of 4.8" by 3.66"



#8 james7ca

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Posted 21 March 2019 - 10:09 AM

Maybe someone might do a camera control software hack to fix that shortcoming.

It's really not a problem for me with my Sony NEX cameras since I already have a very small, battery-powered Bluetooth-to-IR transmitter that is controlled with an iOS intervalometer app (or Android). It was called the MaxStone Bluetooth remote. Unfortunately, the MaxStone is also no longer being made or sold (but I have an extra for backup, since after they were discontinued you could buy them for less than $20). I also have two of the Sony cameras (a 5N and a 5R, where the 5R also went on sale shortly after it was replaced with a newer model).

 

Unfortunately, as I noted earlier many of the new cameras don't offer IR control, they've switched to WiFi so that they can work with smart phones and that means the market for the Bluetooth/IR intervalometers has pretty much died out.

 

What all of the above means is that I can mount one of the Sony cameras to a Hyperstar without using any wires across the scope's corrector lens. You could do the same with a WiFi controlled camera (and the NEX-5R has WiFi), but that uses a lot more battery power and the Sony WiFi apps are (were?) horrible.

 

Also, as djdoud previously mentioned the camera backfocus can be a problem for the RASA, but the Sony E-mount takes only 18mm (although you'd still need a very short adapter). The camera body itself is 4.25" by 2.5" (although the lens isn't centered on the body, so one side extends about 2.9" out from the centerline of the camera body).

 

It looks like Celestron makes RASA adapters for only the Canon and Sony mirrorless cameras.

 

Don't misunderstand, the Sony NEX-5 cameras aren't perfect, but if you are lucky enough to have one they can make a very good and compact solution for grab-and-go imaging.


Edited by james7ca, 21 March 2019 - 10:20 AM.


#9 Cajundaddy

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Posted 21 March 2019 - 10:31 AM

It does depend on the sensor size you need for image scale and focal plane distance.  I have not done this but if Hyperstar were my imaging path I would probably also want a ZWO1600 astro camera to complete the package.  

 

If you really want one camera that does everything, the Olympus EM10 Mk 2 has the same micro 4/3 sensor size as the ZWO1600 with deep capability for long exposure, time lapse, composite, electronic shutter, remote wifi shutter control and a small body.  You can also power the camera via USB cord for all night imaging without depending on the onboard battery.  A very capable camera if you want stand alone imaging without laptop control.



#10 jprideaux

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Posted 21 March 2019 - 08:38 PM

Thanks for the comments everyone. It may be best to just to just go with a dedicated astro camera for the smaller aperture Rasa or CST with hyperstar.


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