Instrumentation and Equipment

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For discussions on all aspects of equipment, from building new devices from scratch, to what ready made products are the best for your current setup. Attached the "Instrumentation and Equipment" observing section.

64 541 By arx 7 hours 39 minutes ago

Photometric Filters - Intereference type Chroma brand

American Association of Variable Star Observers (AAVSO)
dlee Tue, 09/21/2021 - 17:08

I'm looking it to acquiring some photometric filters. I'm interested in the interference type since I live on the west coast of Canada where we have a fair bit of moisture most of the time. I have a Schuler V from a number of years ago and it has the characteristic hygroscopic crusting that happens with the colour glass filters. 

When examining the response curves of the Bessell V and B of the Chroma brand I can see that the peaks of the curves are relatively flat for their range as opposed to the more gaussian "pointy" look of the traditional coloured glass filters.

Error in ASIIMG FITS header

British Astronomical Association, Variable Star Section (BAA-VSS)
Tony Vale Sun, 08/15/2021 - 17:09

 I have recently started using an ASI 183MM Pro CMOS camera for photometry. I started off using the ZWO ASIIMG software for image capture. However on checking the times recorded in the DATE-OBS field of the FITS header, as far as I can see, these  record the end time of the exposure when they should record the start.  If anyone is using this software,  it might be worth checking that the information in the DATE-OBS field is what they are expecting it to be. I have now switched to SIPS which seems to be fine. 


Survey: Who Needs/Received Johnson/Cousin or Sloan Photometric Filters?

American Association of Variable Star Observers (AAVSO)
Richard Berry Sun, 07/25/2021 - 19:02

Hello photometrists--

We're doing a survey to find how many observers are currently looking for either Johnson/Cousin or Sloan photometric filters. If you have recently ordered and/or received filters, what did order and how long did it take to receive them?

Telescope setup simulation software

American Association of Variable Star Observers (AAVSO)
bpablo Thu, 07/01/2021 - 17:57

Hello All,


A colleague of mine, Bhavesh Rajpoot,  has helped write a set of tools for simulating telescope setups. It will help you estimate things like resolution power and limiting magnitude for a new potential setup along with many other things. They are looking for people to try it out and give feedback, so if this interests you, you can find the program  and a more detailed description here:



Bert Pablo
Staff Astronomer AAVSO

On-Axis Guider - How Often Do You Lack a Guide Star?

American Association of Variable Star Observers (AAVSO)
msheald Thu, 06/17/2021 - 11:12

Hello! I'm trying to decide on an on-axis guider vs. guide scope for my new setup.

    For those running a scope remotely or unattended, how often do you lack a guide star using an on-axis guider? I won't be using a rotator since that creates lots of problems with flat fields.

    I use SGPro to acquire images. When the guide star is lost, the program aborts till the time limit of the observation is reached and then the routine goes to the next target. Thank you and best regards.


DSLR characterization

American Association of Variable Star Observers (AAVSO)
SGEO Mon, 06/14/2021 - 21:18

I'm working through the Basic CCD Testing section 8.2 of Richard's Image Processing book, applying the tests to my Canon Rebel T5.

I'm thinking that I have to add some wrinkles to the testing:
   - separate test series for different ISO's
   - Debayer the test images and do each color separately 

Other things I should look out for?

One thing I see with a quick test is that the darks look just like the bias shots... 
I'm wondering if the Canon is doing some tricks for me that I need to understand.

Optical Structures (Astrodon, Jmi, Farpoint) Seeking Investors Sat, 06/12/2021 - 15:32

I received investment information for Optical Structures. They seem to be looking for pre-IPO investors with a goal of doing an IPO within 24 months.

While interesting, I have no idea how that relates to how they will continue, or not, to invest in new products such as photometric filters.

If anyone wishes the documents, I can email them to you.



Question about dark frame scaling -new CMOS cameras

American Association of Variable Star Observers (AAVSO)
RGN Sun, 06/06/2021 - 10:06

I would like to know if dark frame scaling is possibile with new CMOS cameras in the event of a camera that shows zero amp glow such as the QHY600 or QHY268. Since the electronics of these new cameras are also very stable I wonder whether one could even skip master frames and just subtract one single dark frame of corresponding exposure or one single scalable dark after subtracting a single bias. Of course gain, offset and temperature match the ones of the calibrating frames.