A modified DMK nosepiece for Solar imaging & PSTs

[DrRobin]

Hi,

Sorry to post in this section, but this is specific to solar and also PST.

My new DMK41 can't quite image the sun in one go when used in a Lunt 60 (500mm focal length). I tried a 0.5x focal reducer on the end of a short nosepiece but this gives rather too much reduction, resulting in a lot of wasted pixels. What I needed was a way of getting the focal reducer closer to the chip to optimise the use of the chip.

The same happens with a screw in Barlow, it gives slightly too much magnification (PST users note) and getting the 1.25" screw in Barlow close will reduce the magnification and might allow a DMK to focus in a PST at near prime focus without modifying the PST eyepiece holder.

The DMK nosepiece is threaded all the way down with a 1.25" filter thread, so a qucik go with a hacksaw and a IS standard nosepiece was reduced in size.

The following pic shows the standard and chopped down nosepiece.

I chose to chop quite a lot off as the optimum distance can then be achieved by adding the C/CS spacer, shown in the pic next to the chopped down nosepiece.

And finally, a 0.5x FR fitted. Notice how close it will be to the body of the camera.

I haven't seen the sun yet to test it, but I reckon this will be somewhere near to the 0.7x I require.

[Montana]

Thanks for this info, I'm sure others will find it a lot of help. I hope it works

Alexandra

[Photosbykev]

If I placed my DMK41 front casing up against the top of the PST eye piece tube I reached focus on the sun with a couple of millimetres to spare, others have had focus problems with the same equipment so there must be some variability in the manufacturers quality control and consistency