Tuning a Coronado PST

[Space Cowboy]

The manual makes no mention of tuning the PST but I believe you have to turn the black collar at the base of the OTA to maximise surface contrast on the solar surface depending on the temperature. Is this correct?

[Gazabone]

That's correct, as you tune the scope you'll see features appear and disappear. On my pst, it needs to be turned almost all the way anti clockwise (as stood behind the scope) for the proms and filiments to appear at their best, turning it clockwise (almost as far as it goes) seems to show sunspots better. I'm not sure whether these really are sunspots, I've not put my white light set up side by side to compare. Hope this helps :-)

[Space Cowboy]

Cheers!

I've had the PST for 6 months and only just heard about this! The manual says "the focus knob is the only external device you will ever need to adjust"

Why don't they mention the tuner? Bizzare!

[JamesF]

Especially as the etalon tuner ring is not only movable, but adjustable in its own right.

James

[Space Cowboy]

I remember looking at the collar when I first got the scope thinking it was adjustable but then reading what the manual said I thought I'd better not touch it!

[Space Cowboy]

Its like driving a car before realising you can move the stearing wheel!

[Peter Drew]

Could well account for some disappointed accounts from first time users. Always worth experimenting with as retuning can often produce surprising results. Tuning that is way off will show the sunspots albeit in red. 

[Moonshane]

In my PST mod, I tend to have the etalon all the way to the 'left' from behind the scope. I then use the sweet spot as my tuner. in the central regions and to the left of view you see lots of detail, to the right you see lots of sunspot detail.

[Space Cowboy]

Thanks! Its good to know there is potentially better detail to reveal. I've noticed all my images have lacked detail or contrast on the right side of the image.

[Moonshane]

that will be the sweet spot.  think this is one of the main challenges of knitting together frames from psts.

[keithatrochdale]

Space Cowboy you must come up to the Astronomy Centre on a Saturday afternoon when sunny and try a few Ha scopes and have a chat.

You will find that there is a sweet spot and you need to move round to get the best detail. I find that a 10 mm eyepiece is about the best size, but will vary with seeing conditions. We tend to use zoom eyepieces and the Seben 8 - 24 mm works very well for about £50, it is very useful addition to be able to zoom in and out.

Hope to see you soon.

[Space Cowboy]

Cheers Shane!

Thanks for the invitation Keith! I am mostly imaging with the PST and my last image is on this thread :http://stargazerslounge.com/topic/243021-solar-ha-april-26th/#entry2639105

[Moonshane]

That's classic sweet spot with more detail on the surface/less on the spots left and centre and vice versa on the right.

[Space Cowboy]

Thanks Shane I managed a quick session this evening despite the wind and passing clouds. The tuner was all the way to the left and as I moved it clockwise the proms on the right side of the disk popped out greatly.

[Merlin]

An annoying feature of some PST etalons is that the tuning ring doesn't turn far enough to give maximum H-a tuning.

The solution is to remove the rubber ring and the outer metal ring ( marking the original position ), and reposition the metal ring a screw hole or two further on, then, replace the rubber ring.

[keithatrochdale]

Cheers Shane!

Thanks for the invitation Keith! I am mostly imaging with the PST and my last image is on this thread :http://stargazerslounge.com/topic/243021-solar-ha-april-26th/#entry2639105

I assume you know of this site;

http://solarchat.natca.net/index.php

Would be good to get together and you could maybe give us some advice on imaging?

.

[Space Cowboy]

Oops missed these posts. Thanks Merlin for that info!

I can give advice on planetary imaging Keith but solar is very much a new world for me.Not on any Solar forums yet.

[Stu]

An annoying feature of some PST etalons is that the tuning ring doesn't turn far enough to give maximum H-a tuning.The solution is to remove the rubber ring and the outer metal ring ( marking the original position ), and reposition the metal ring a screw hole or two further on, then, replace the rubber ring.

I did exactly that on my PST. Very simple but effective

[JB80]

Yep, same here, moved it over a knotch.

The sweet spot is a right pain when it comes to imaging, it makes mosaicking a nightmare in the mod but is less of a worry for single frames as you can get the feature fairly well centred in the spot.