Watching the Sun

[trent_julie]

Hey all,

Just got myself a Coronado PST and I have a couple of questions that I hope the forum can help me with.....

1. When is mercury due to transit the sun next and how often does this happen?

2. How to achieve prime focus without a powermate/barlow? (as I had massive troubles today with this method)

Cheers

Trent and Julie

[Matt Wastell (Matt)]

Hi Trent and Julie

Not sure about prime focus but Mercury and Venus transits -

Mercury
2016 May 09 14:57 319"
2019 Nov 11 15:20 76"
2032 Nov 13 08:54 572"
2039 Nov 07 08:46 822"
2049 May 07 14:24 512"
Venus

[Matt Wastell (Matt)]

......Venus
6 June 2012 - and then it will not happen for another 100 plus years!!!!!
Good news - in Australia we will see the entire transit!
An event not to miss.

[trent_julie]

thanks for that info...

We are already planning on the Venus transit, in fact thats the sole reason why we now have the PST, Just have to find the place with statistically the least amount of cloud, apply Murphy's law and avoid said place.......

Mercury transits happen a lot less than I imagined in that case. I guess its a good reminder of the word assume...................


Thanks for your response Matt, much appreciated

Trent & Julie

[csb (Craig)]

For prime focus it depends on the camera you are using.

I use a DMK21 CCD camera made by The Imaging Source.

I can achieve focus, on my PST, by using an adapter that allows the chip (in the camera) to be positioned closer to the eyepiece.

Some adapters have a ridge around the edge that is too big to go inside the eyepiece holder and so the imaging chip is to far away to achieve focus.

If you are having trouble finding a suitable adapter then perhaps you can grind the ridge off (if that appears to be the problem).

[Paul Haese]

The problem with a PST is that the back focus is just too short for imaging. However, you can as has been mentioned use a DMK with a short profile adapter. DSLR cannot be used at all.

[daveg (Dave)]

As the guys say, Best way to image the Sun is by taking a video with said camera (DMK21 etc) and then use registax freeware to pick out the best frames and stack them together.

The closest I got to prime focus was to unscrew the lens from my Televue 3x barlow (this gives about 1.5x) - pop it into the eyepiece holder of the pst then put the DMK on top. These lower powr lens only systems are available in europe heres the type of thingy to look for... With this you may also get focus with DSLR
http://starizona.com/acb/15x-Piggy-B...-P1317C80.aspx

what type of cam are you using??

BTW theres a nice active region (sunspot) to get practicing on at the mo. Up here in Ireland at this time we struggle to see the sun at all..

David Gradwell

[trent_julie]

Thanks for everyones help.

I made an attempt using a 5x and also a 2.5x powermate on a Canon 1000d and then used "EOS Movie record" to capture video/stills.

This I feel is where I ran into troubles by asking for too much magnification from the PST.
A quality image could not be achieved, the result from stacking was terrible to say the least.

I've been considering getting a OSC, but this maybe some time off yet
below is a link displaying what video i did capture using the method described.

Thanks again for everyones help




www.youtube.com/watch?v=TEVG_buee94

[trent_julie]

DaveG,

Thanks for the tip on the piggyback barlow, I shall make an effort to get one at sometime soon


CSB & Paul,

We will look more into the DMK, Seems like the go.

Thanks Heaps

Trent & Julie

[trent_julie]

Hi all,

I received my piggyback barlow from Starizona today (very quick delivery) yet as any astronomer would know, clouds don't care for new equipment so I will post the results as soon as i get them,

I'm also considering chucking an IR blocker onto this chain, as it has been recommended elsewhere to do so on planets....

Any thoughts on this?
If yes, I assume a v-blocker filter will have the same effect...

Cheers

Trent & Julie

[Merlin66 (Ken)]

T&J,
The light from the PST etalon/ BF is tuned to Ha there are no other wavelengths getting through so any additional filters would do nothing.
I haven't tried it but maybe a transfer lens ie very low power eyepiece projection where the camera body is positioned as close as possible behind the eyepiece would allow you to focus without excessive magnification. The PST works at f10 and the optimum f ratio is around f30 so a maximum of a x3 Barlow would be the limit.
I use a DMK21 with very good results......

Ken

[trent_julie]

Originally Posted by Merlin66

T&J,
The light from the PST etalon/ BF is tuned to Ha there are no other wavelengths getting through so any additional filters would do nothing.

That would be a very "duh" moment to me............ thanks for stating the obvious.... kicking myself already

As for the barlow, I've used a 2.5x powermate in combination with a DBK 31 (not a 41) without success.

I have also now found an earlier thread that suggests dismantling the PST slightly, whilst this is well within my capability the mere thought of pulling the PST apart does not sit well with me (new toy and all), consequently I'm really hoping this piggyback barlow(1.5x )works out, the website says its ideal for webcams and PST's

thanks for the info on the optimum f ratio, I had no idea until now.

Cheers

Trent and Julie

[trent_julie]

OK,

So after much mucking around and imaging between clouds I have finally got my first stacked and processed image of the Sun.

Equipment
Coronado PST
1.5x piggyback Barlow
DBK 31 Webcam
HEQ 5 mount

Settings
130 Frames Stacked and processed @
Brightness 1
Exposure 1/313
Gain 328
Gamma 0

Thanks for everyones help

Trent & Julie

[csb (Craig)]

A good choice of camera. For imaging the sun in Ha, I think the DMK/DBK series isone of the best. A google search of images shows that images taken with these cameras are the best overall, imo.

Now just a few more years, maybe, for the sun to put on a show.