PST - questions

[Photiost]

Hello, new member here, this is my first post.

Just purchased a used PST (came with a Zhumell 8mm-24mm zoom) and I have some questions.

Using the zoom at the 24mm setting I find the image very nice and clear but the telescopes AFOV is quite small - is this normal?

I find the best views are when I keep the image near the centre of the eyepiece however the eyepieces AFOV always stays much larger than the

telescope AFOV - I cannot get an image without "some" vignetting - t Is this a common occurance on all PST's ?

I also tried using other eyepieces (plossls + Orthos) 8mm 11mm 12.5mm 13mm 15mm 18mm and 21mm and although both telescope + eyepiece

AFOV's seem to get closer with the higher magnification eyepieces .. they never seem to meet.

Nor sure if I am making sense here but with all my other "regular" Reflector + Refractor telescopes I do not have this vignetting problem.

I also noticed that when I tune the scope for prominences, I am able to tune near the centre of the solar limb or slightly higher or lower -

then by moving the disk to the "tuned sweet spot" the images are excellent.

Thanks !

[Peter Drew]

It is the small aperture of the blocking filter, 5mm in the standard form, that is causing the field of view vignetting. This is a normal consquence of the system. It is possible to upgrade the blocking filter with a 10mm or 15mm one but this would set you back more than the value of the PST.

[Photiost]

Thank you for explaining that it is the small aperture of the blocking filter ( 5mm ) which is causing the vignetting.

It is a little annoying, but I am relieved to hear this is the norm - I was wondering if something was "not quite right" with my unit.

For the tuning:

I suspect it is also normal that we tune a sweet spot and move our target areas through that spot to get the best resolution ?

On my sample, at the 16mm zoom setting, I have tuned it to the central part of the solar disk so all prominences left and right are sharp with lots of details ...

The remaining prominences on the upper and lower quadrant however are almost visible and only come to life when I turn the knob (eq mount) and move those quadrants to the tuned area.

I have also discovered that the only time I can tune the entire solar disk is at the 24mm zoom setting but the image (though sharp) is quite small.

At the 24mm zoom setting (the eyepieces AFOV is only 40 degrees) the small blocking filter aperture is quite evident and the solar disk has to be centered perfectly.

At this setting I can observe the entire disk surrounded by prominences which are tuned and sharp.

[Peter Drew]

Sounds lile you are doing everything right. Next step, a PST mod.

[Photiost]

Thanks again.

I am planning to attend the local Astronomy clubs next Solar observing outing so I can observe with other PST's and make the comparisons.