Skip to content
Calibration : Part I - Pre-processing | Hyperion Astronomy

Calibration : Part I - Pre-processing


Calibration frames are used to correct for optical defects in the imaging train such as: hot pixels, cold pixels, dead columns, vignetting, and dust motes. This process is indispensable in applications such as asteroid photometry. These frames are classified into three separate categories:

  • Bias frames :

With the cap on the lens or telescope, we take the shortest exposure possible. This tells Prism that there is no light coming in and all the noise present is inherent to the system's electronics themselves. Bias noise is also available in dark and flats frames and needs to be taken out.




  • Dark Frames :

Also taken with the cap on the lens of the telescope, dark Frames differ from Bias Frames in that the exposure length needs to match that of your light frames (example: 5 minute exposures of galaxies or nebulae). It is important to remain consistent between the light and darks when it comes to binning (CCD and CMOS cameras), ISO (DSLRS), exposure length, and temperature. Prism can use your bias frames to compensate for differences between you lights and darks in case they differ slightly.

  • Flats Frames :

Just like the other types of calibration frames, Flats are required to correct for optical issues that reduced the light throughput like: dust most, vignetting, etc.  A good calibration frame can even out the light in the light frames and produce a flat field free of dust doughnuts and light fall-off if the corners.

Importance of calibration frames

The importance of calibration frames becomes obvious when dealing with cosmetic and scientific imaging. With the latter, it is imperative to remove a maximum of the polluting factors (hot and cold pixels, motes, gradients) inherent to astronomical imaging systems. This becomes quite evident in photometric measurements which we will demonstrate in later tutorials.


Both pre and post processing tools are available in all versions of Prism, allowing calibration of data immediately after you acquire it. This negates the need for multiple software packages and reduces the learning curve. Prism is designed around power, compactness, and ease of use. 

Video tutorials
Please view this video tutorial that explains calibration frames. Do not forget to expand the video to fullscreen and take advantage of the higher resolution.




Previous article The precision of plate solving
Next article The precision of plate solving

Leave a comment

Comments must be approved before appearing

* Required fields

★ Reviews

Let customers speak for us

19 reviews
Exceptional Mount

A couple of years ago, I wanted to replace my old VMA200 mount with something more modern.
While visiting the Paris Astronomy show (RCE 2012) I noticed the Nova120. At that time, it was a brand new offering that I have not seen before, hence my hesitation to purchase
I wanted to purchase a E.U product to guarantee the quality and ease of access to support in my own language. I checked the forums and heard nothing but good things about the Nova120 so I decided to purchase it.

I have used enough astronomical instruments in the last 30 years to know what great quality is. The Nova120 coupled with the PRISM v10 and a CDK20 (508 mm) helped me pull off 900s unguided images with great ease. (Raw FITS File here). Payload of this setup is about 80 kg (160 lb).

The dizzying slew speeds, excellent accuracy and painless tracking makes this hobby easy and enjoyable again.
After using this setup for a year and a half, the only problem I had was rebalacing the gear after changing scopes. The superb electronics and software included make this tasks even more easier that just eyeballing the scope for movement due to unbalance.

You can very easily watch the motor consumption and know where the unbalance is....that easy. I have so much data that it is becoming difficult yo keep up.
I have absolutely zero regrets, this purchase has made everything easier: No summer/winter worm-gear adjustments, no guiding... just start imaging night after night after night.

Eric Barbotin

Imaging Made Easy

Prism is my GoTo program for observatory control and imaging. Prism's many features make imaging taking a breeze.

I was concerned about giving Prism a try , especially as its quite expensive. So far Im very impressed and glad of my decision.
Im a beginner at all this so haven't tried other more recommended software, Prism appealed as it seems to do everything instead of using several programs 👍🏻

Great lightweight guide scope

This guide scope replaces a 400/80 that was waaay too heavy for what it did. The smaller 60mm scope does a great job guiding and I can RA balance with just one counter weight now - much better - and it looks like something Ferrari designed

Still learning Prism using Wireless links...

I have much of your software working at this time... I have it parked on my main computer, and a notebook... My main computer is a OverClock computer with 32 Gigs of RAM Clocking presently at 4400MHz with software parked on SSD drives... The rotation dome by NexDome is still not working... Most problems like this have to do with ASCOM Drivers... There is not very much detail information on how to use this software... I have to feel my way to a total operational staus... Second issue... The rain in the San Francisco Bay Area this year has limited my access to my larger telescope (12 inch SCT)... This rain has been so significant, I was force to weatherize my observatory... My goal here is,,, I am trying to remotely control my observatory totally. I have used Netgear Powerline 2000 to handle camera images and discover controlling rules to do that... High speed is vital for images with cameras over 3 Megs... I have both 12 Mega sensors and 24 Mega sensors... I am also using Netgear Nighthawk router and its mating extender to increase control signals to my observatory that is about 100 feet on the side of hill... I am also using Virtual Here software on a Raspberry Pi inside the observatory to solve the USB interface requirements... I started out using Model B and B+ on level 3 raspberry Pi's... I have moved to Level 4 Raspberry Pi to gain access to USB 3.0 technology... Big difference! I hope by early spring to have everything working... Bob Ritter MicTechS