> IR-cut filter removal improvement on Pentax K5

  • Posted on: 8 March 2019
  • By: tihomiry

I am so impressed with the K5 ability to quickly gather signal from nebulas (Quantum efficiency) and galaxies, so I decide to take one more K5 and to remove the IR-cut Filter of the old one. The same thing I have done in the past with Pentax KM and I got significant improvement of 2.5 stops. Here is a short article on that: http://planetarium-gb.eu/pentax_astrophotography.pdf
Since I have K5, I almost stop using KM as K5 has huge advantage in terms of QA and noise levels. There is no amplifier glow and no need of dark frames and cooling.
In fact K5 is one of the best DSLRs for astrophotography which is using Sony IMX071 Xmor CMOS sensor. Same as ASI071MC Pro (color) (https://astronomy-imaging-camera.com/product/asi071mc-pro)
Thus after the modification the Ha sensitivity improvement is far less then what I expected. But this camera is great unmodded, so it seems that Pentax IR-cut filter is letting most of the Ha spectrum to the sensor. Below is comparison of M42 Orion nebula with UHC-S filter of 1.Modded (without IR-cut) K5 and 2.Unmodded. There is very slight difference but well enough to show far great results, when push it to the limit with a fainter objects and stack of 100+ frames.

For my last trip to the Rodopa mountain I decided to cross the limits and to target an object that is hard to believe that a non-professional equipment could catch.

While cleaning up my PC I found sequences of shots of Virgo galaxy cluster taken during springs of the last 2 years. Those were attempts to shot this object, but I was not satisfied with the result and left them.

I recently bought a pocket spectroscope for laboratory use. You can find it at Ali for 5$. It is with glass prism and well build. So I did some test to use with a telescope but did not

http://www.deepskywatch.com/deep-sky-hunter-atlas.html This is an amazing resource. Detailed atlas of all the sky with NGC and IC objects.

Reading a new product that claims to be 100x time more powerful then conventional telescope, I realise that this is just an astrograph with a digital camera that is doing stacked images and show them trought eyepiece or App.

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