PST+zero power 'Barlow'

[nytecam]

Hi - can't quite reach focus with my Asda webcam in the PST and the normal way to resolve it is to use a Barlow to extend the focus outwards. This, whilst allowing focus to be obtained, increases the image scale so less of the sun is recorded.

Tried an alternative this morning and it seemed to work without apparently changing image scale:hello2:

Placed a couple of standard filters eg 1-1/4" red+IRblock into PST drawtube immediately on top of the scope's rejection filter and replaced webcam. Focus now achieved with some leeway!

If I recall a plane-parallel plate/filter in a convergent beam 'delays' the coming to focus slightly and it works for me. Anyone tried it on this or other applications or is it common knowledge?

[RikM]

I've not tried that but it sounds great. Any chance of some pics?

[nytecam]

I've not tried that but it sounds great. Any chance of some pics?

Not for moment - achieving focus was major! Auto webcam and drifting cloud across sun so impossible to image:mad: Seen some fleeting proms and flares around active sunspot on laptop screen

[Merlin66]

Maurice,

Yes, the increase in back focus (by about 1/3 the thickness) when a plate is positioned "in the converging beam" is handy to know.

It also affects the focus when using a Star Analyser...and when you remove the filters from your camera for an "Astro" Mod

[nytecam]

Thanks Ken for confirming filter effect on focus

Not for moment - achieving focus was major! Auto webcam and drifting cloud across sun so impossible to image:mad: Seen some fleeting proms and flares around active sunspot on laptop screen

My first attempt to use Asdacam on sun via PST passed through Registax - complete novice at this but more recorded than seen through my old eyes at the EP:hello2:

[badgerchap]

Nice. Beats the pants off my attempt today - although tbh no pst here!

[nytecam]

Thanks BC - here's a couple via PST CaK - I completely blind to far violet of CaK line but my cam can

ps: All these shot through the lounge double glazing - too much hastle to shift gear outdoors and trying to see laptop screen - so I'm happy:cool: