From: "milton_aupperle" <milton@outcastsoft.com>

Date: February 10, 2010 11:41:12 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: PGR Grasshopper Review - 8 months later


Hi Folks;


I have been having a back and forth e-mail conversation with PGR on some issues with my EXView HAD Grasshopper (GRAS-14S5M-C) and I thought I'd bring this out so everyone knows what the score is. They are very expensive cameras and people should know about them before plunking your money down.


Firstly, I could never figure out why my Red response with the camera was not as good as say the StarLight Express SXVF H9C or other Microscopy and Astronomy cameras that use the Sony ICX285AL CCD. I have to expose my Red filtered  images by about 65% longer to get correct RGB balances. As it turns out, there is a special "enhanced near infrared mode" that many low light manufacturers have implemented, but not PGR. What this means is that the Quantum Efficiency for the Grasshopper at the DSO significant wavelength of about 656 nm is about 1/2 of what it could be than with other low light cameras with the same Sony CCD, so it's ability to capture faint nebula is not nearly as good as it could be. PGR has told me that this may be implemented in there Grasshopper 2 models, however I'm not holding my breath on that.


This leads to the amp glow issue, which all the Sony CCD have and ramps up rather gradually as you increase exposure time. Basically you get a light glow on the top left and to a lesser extent top right corners of the image. Other Camera manufacturers have turned off the amplifier during the exposure which produces nice flat evenly illuminated images. This can be reduced using dark frames, but it means faint nebula features will get lost in the glow on the top side of the CCD. Oddly enough the TI based Unibrain cameras did allow me to shut down the amplifier and the processing side of the chip set via a register, which reduced camera heat too. I have been requesting this feature from PGR for several years now.


Thirdly, the Grasshopper generate a lot of heat and will rise a minimum 7°C above ambient temperatures after running for just a few minutes. Unless the camera is cooled, you basically can not do DSO imaging over say 60 second exposures without a lot of CCD noise. It would have been nice if I could power things off in the Camera when I'm doing longer exposures, but that isn't possible as there is only one power register I can work with, so can't power different parts of the chips down. If your not going to cool the camera, then your not going to be able to much as far as DSO images go.


Lastly shutter exposure control has always been a sore point for me as a developer with PGR. Instead of implementing it like TIS and other manufacturers where I just set the long exposure (up to 60 minutes) in a register, I have to set up loops and timers and a whole complex system to get "Bulb" trigger to work properly on PGR cameras to do a long exposure. And the end user still has to connect up pins on the Hirose I/O connector properly too, so it's just a PITA to deal with.


On the plus side, they are fast for frame downloads (i.e. 15 fps for a full 1384x1036 16 bit frame versus 4 seconds per frame with Starlight XPress), are quite compact (would fit in your shirt pocket), are very light weight (only a few ounces), have two FireWire ports so you can daisy chain cameras together to reduce cable clutter (can't do that with USB), is bus powered so no additional power source required and offers ROI capabilities too. If you build your own cooler and cool the camera down, you can reduce the noise and do some reasonably deep DSO imaging as I have done. But I have been told by PGR they have no plans to address the poor QE for near infra red and amp glow for the "Version 1" GRAS-14S5M-C cameras, so caveat emptor.


So if your looking for a deep (15+ minutes) DSO camera, the Grasshopper GRAS-14S5M-C isn't a great choice and your better off looking to SBIG with Darryl Roberton's Mac Equinox Image:


http://www.microprojects.ca/equinoximage.html


or  Starlight XPress cameras using Jeff Terry's iCCD software:


http://www.iccd.us/


HTH..


Milton Aupperle