UPDATE FROM MABULA
I have had a very rough 2 months unfortunately health wise. I was struck 3x in a row with bacterial infections. The second infection occurred after a routine hospital checkup and I became very sick. I had to rest and take a lot of antibiotics. Once I was recovering and restarting work 1 month ago, I again became sick. The infection was not yet gone, so even more antibiotics and rest was needed. Needless to say, it took a lot of my energy and I needed a lot of rest.
Finally, the infection is really gone and my energy is coming back step-by-step now and I have started work again. I am terribly sorry to have kept you waiting for support. I will address all outstanding questions and e-mails step-by step and will be on the forum daily from today.
APP 2.0.0-beta47 will come soon as well, a lot of work was already completed before I became very ill, so the release is also nearly ready for you. Beta47 will be much faster actually. Many workflows will be more than 2x faster, mosaics can even be 10x faster than before because registration really received a major boost... all compared to beta46. Before I release it, I will make sure that everything is working properly and then I will release it.
A total of 19 x 180s Light frames captured using BYEOS with my modded Canon EOS750D & wedge mounted Celestron CPC9.25 and attached 0.63 Focal Reducer.
Processed in APP with Darks, Flats & Bias with the diffraction spikes for the two main stars HD75700 & HD75638 added in PS.
![M67 (NGC2682) [2019.02.25][FLICKR]](https://i0.wp.com/www.astropixelprocessor.com/wp-content/uploads/wpforo/attachments/892/1801-M67-NGC2682-20190225FLICKR.jpg?ssl=1 "M67 (NGC2682) [2019.02.25][FLICKR]")
Thanks for looking..,
Kirk
Beautiful image! I love the colours of the stars.
If I may ask one (possibly sensitive) question: are you sure the back focus between the focal reducer and the camera is correct? The stars in the corners look a bit elongated which suggests the back focus is too small at the moment.
Beautiful image! I love the colours of the stars.
If I may ask one (possibly sensitive) question: are you sure the back focus between the focal reducer and the camera is correct? The stars in the corners look a bit elongated which suggests the back focus is too small at the moment.
Thank you for the kind words @wvreeven
No, your question is not sensitive at all. I am always looking for ways to improve what I am doing and am open to suggestion and tips.
So, if I give you my setup details please do check if I have things done correctly.
First off I use this formula to calculate my Focal Length & Focal Ratio: http://www.wilmslowastro.com/software/formulae.htm#FR_b
EQUIPMENT
Celestron CPC9.25 SCT
Celestron f/6.3 Focal Reducer
SX OAG & Filter Wheel
Canon EOS 750D
CURRENT SPACINGS
From my SCT to the Focal Reducer 49.25mm (via Baader SCT > 2" Click-Lock & 2" > SCT Nose Piece)
From Focal Reducer to DSLR 53mm (via 3mm Rubber Gasket as Focal Reducer fouls OAG Prism > SX OAG & Filter Wheel > 7.5mm Spacer Tube)
From 7.5mm Spacer to DSLR Image Plane 55mm (via Baader Protective T-Ring 298550 & Canon EOS750D)
Regards..,
Kirk
Beautiful image! I love the colours of the stars.
If I may ask one (possibly sensitive) question: are you sure the back focus between the focal reducer and the camera is correct? The stars in the corners look a bit elongated which suggests the back focus is too small at the moment.
Thank you for the kind words @wvreeven
No, your question is not sensitive at all. I am always looking for ways to improve what I am doing and am open to suggestion and tips.
So, if I give you my setup details please do check if I have things done correctly.
First off I use this formula to calculate my Focal Length & Focal Ratio: http://www.wilmslowastro.com/software/formulae.htm#FR_b
EQUIPMENT
Celestron CPC9.25 SCT
Celestron f/6.3 Focal Reducer
SX OAG & Filter Wheel
Canon EOS 750D
CURRENT SPACINGS
From my SCT to the Focal Reducer 49.25mm (via Baader SCT > 2" Click-Lock & 2" > SCT Nose Piece)
From Focal Reducer to DSLR 53mm (via 3mm Rubber Gasket as Focal Reducer fouls OAG Prism > SX OAG & Filter Wheel > 7.5mm Spacer Tube)
From 7.5mm Spacer to DSLR Image Plane 55mm (via Baader Protective T-Ring 298550 & Canon EOS750D)
Regards..,
Kirk
This got me wondering if in fact I had an error somewhere in my calculations so I uploaded a single raw frame from this set of data to Astrometry.net and was given a PixelScale of 0.536 arcsec/pixel
Using the formula:
fRatio = (pixel size [um] x 206.3) / (aperture [mm] x arcsecPixel)
fRatio = (3.7 x 206.3) / (235 x 0.536)
fRatio = 763.31 / 125.96
fRatio = 6.1 rounded with an effective Focal Length of 1424mm
This is obviously below the f/6.3 that using the website formula in the above post gave me, so I have slightly too much space between the Focal Reducer & my camera's image plane than is ideal.
I cannot say if the website I used for calculations has incorrect values or if it is in fact a slight variation in my actual Focal Reducer.
I am more inclined to trust the arcsec/pixel value produced by Astrometry.net
With this in mind I have calculated that I was over spaced by 6.25mm and have now rectified this by placing an order for some very fine spacer rings and I will be able to reduce the spacing by around 6.3mm.
When the items arrive & the first available time to image after that, I will upload to Astrometry.net again to check.
Overall though I do not think that I will get a true flat field across the whole frame as this is a limitation of the Focal Reducer not being a true Flattener.
Regards..,
Kirk
I agree that trusting the value given by astrometry.net is a sensible thing to do. I have come across slightly erroneous specs too often (and sometimes very erroneous specs!) and have developed a mistrust for them. My advise would be to take the specs as a guideline and play with the spacing until it is right. The only way to do that is to painstakingly take pics and adjust the spacing until the stars are to your satisfaction 🙁
