OIII vs continuum?

[Thalestris24]

Hi all

I've no doubt this has come up before but I wonder if anyone has done a comparison between the two? I'm a newbie solar imager and am looking to improve my white light imaging... (Anything would be animprovement!). I was also thinking that if the OIII works ok with solar then I could use it for night-time too

I imagine both are quite dark when used with ND5? Are there any difficulties with being able to see to focus the OIII filter? I understand the solar continuum filter needs a good IR cut filter when imaging - but can get away without with the ccd-OIII?

Thanks

Louise

[Steve Ward]

Hi Louise , 

I always use an OIII filter in the mix for my full disc DSLR images , helps considerably with the Contrast and Granulation , but I am using the ND3.8 Imaging film to keep exposures at a reasonable level , the ND5.0 will mean longer exposures.

I use it over a Continuum in this set-up purely because I already had one in the box of bits and it did the job which saved me spending another £100 on a 2" Continuum ... 

For the Close-ups with the wedge and Mono webcam I splashed out on an 1-1/4" Continuum and in conjunction with a UV/IR Block it's a winning combo.

Give the OIII a try with various settings and see how you get on , contrary to popular belief you do not need to be at 1/1000 - 1/2000s @ ISO100 , I rarely get above 1/400 @ ISO200 and have got good crisp detail right down at 1/60s before now when shooting through cloud  , as I've said before though the most critical point is nailing the focus .

[Thalestris24]

Hi Steve

Thanks for that. Problems with getting focus is one of the reasons I was considering a narrowband filter. I've been trying to image with my ST80 and sharp focus has eluded me. I've been trying with a cls-ccd and a UHC but still can't quite get it . Wondering if the solution might have to be a better scope...

Any recommendations?

Cheers

Louise

[Steve Ward]

I would make a full aperture filter for the 150PDS , two benefits , the dual speed focuser will help considerably with your focusing issues and the extra aperture will let you keep exposures shorter with the ND5.0 + OIII combo ... 

[Thalestris24]

I would make a full aperture filter for the 150PDS , two benefits , the dual speed focuser will help considerably with your focusing issues and the extra aperture will let you keep exposures shorter with the ND5.0 + OIII combo ... 

Hi Steve

Well they are both F5.. I don't really want to use the 150pds for solar. Maybe an ED80 would be better than the ST80?

Cheers

Louise

[Steve Ward]

The Tal 100RS is a great 'scope for Solar , I use one exclusively for my Solar stuff now ... 

Cheaper than an ED80 by a considerable margin ... 

[Thalestris24]

The Tal 100RS is a great 'scope for Solar , I use one exclusively for my Solar stuff now ... 

 

Cheaper than an ED80 by a considerable margin ... 

Yeah that looks like a nice scope - but F10... If I were to buy another scope I think I'd want to be able to use it for DSOs too

Cheers

Louise

[DrRobin]

The ST80 with its 1:1 focuser is not ideal against a 10:1 and couple that with trying to focus on the camera and with no tracking makes it a very difficult job. I am not sure if a filter will help with focus, unless it is IR that is spoiling the image?

I have used my ST80 with a DMK41 and a '21 sized webcam before on an unguided mount, but you need one run to focus and then another to get some images and I takes a lot of time.

I am considering changing my solar set up and get an 80 or 90mm achromatic, probably one of these as soon as they are back in stock.

http://www.rothervalleyoptics.co.uk/rvo-90mm-f500-achromat-refractor-ota.html

It won't be brilliant at DSOs as it is not colour corrected, but should give very sharp views at night and during the day it won't make any difference. They are a good deal cheaper than anything else.

Robin

[Thalestris24]

Hi Robin

Yeah, I need another mount! Trying to image from a wobbly camera tripod isn't easy! Even so, every attempt I've made to get sharp focus has failed! The 1:1 focusser doesn't help but there doesn't seem to be any point where the sun is in sharp focus. I don't _think_ it's IR - I've fitted a cls-ccd and a uhc filter (both together!) and they have IR cut built-in. The cls cuts UV up to 400nm and IR from 700-900nm. I have to admit I'm not sure about after 900nm. The 1100d I've been using is unmodded. I would have thought that between them the IR would be sufficiently cut?

Anyway, as regards another scope, surely it's worth spending the extra for say a SW Evostar 80ED? Only £349 for the basic OTA and with a 600mm focal length, plus a great reputation. Of course, I'd really need a second mount to put it on! But that applies anyway.

Edit: I should mention I've latterly been using a x2 Barlow, so that probably doesn't help either! I'll try again without...

Cheers

Louise

[DrRobin]

For solar, an ED80 won't make much difference over a simple achro, but it would for night time and if you are looking for a dual purpose scope then it would be a good idea. 

At Christmas, with a little help from the misses and and my parents I bought a WO 102mm apo and matching field flatener, I went for it to use at night time as well as solar.  Has it been used outside the hours of daylight?  No, and the field flatener has never been out of the bag.  Now I know the cost is much more than an ED80, but I decided that I should buy something for one task and use it for that rather than somethig that seldom gets used for what it is best at.  That it is the reason, I am looking at the RVO scopes, nice and simple, small and light, but 10:1, 2" focuser and decent optics.  To nick a phrase from Ronseal, 'it does what it says on the tin'.

Robin

PS, I often get it wrong, so ignore all of the above if you like.  An ED80 would probably do me nicely as well.

[Thalestris24]

   

For solar, an ED80 won't make much difference over a simple achro, but it would for night time and if you are looking for a dual purpose scope then it would be a good idea. 

At Christmas, with a little help from the misses and and my parents I bought a WO 102mm apo and matching field flatener, I went for it to use at night time as well as solar.  Has it been used outside the hours of daylight?  No, and the field flatener has never been out of the bag.  Now I know the cost is much more than an ED80, but I decided that I should buy something for one task and use it for that rather than somethig that seldom gets used for what it is best at.  That it is the reason, I am looking at the RVO scopes, nice and simple, small and light, but 10:1, 2" focuser and decent optics.  To nick a phrase from Ronseal, 'it does what it says on the tin'.

Robin

PS, I often get it wrong, so ignore all of the above if you like.  An ED80 would probably do me nicely as well.

Hi Robin

Well if you still have the apo and not using it...  From my point of view the solar imaging isn't a priority - it's really something to do in the summer and when the sun's out, which isn't that often up here! Still, it's nice to do in the daylight (being a daywalker as well as a creature of the night ). I'm sure I'd get more use out of an ED80 and it should be relatively easy to guide.

Took the barlow and the UHC filter out of the ST80 this afternoon and just did a test on some distant buildings. Still couldn't get what I'd judge to be a very sharp focus. So it's either a limitation of the focusser or poor optics in the scope. In either case, it's not going to be much use for solar imaging so I'll have to have a think. I've been contemplating getting an Advanced VX and an ED80 but together they would be a significant outlay. Hmm...

Cheers

Louise

[Merlin66]

I use the ED80pro with a SM60 Ha filter (and sometimes the Baader wedge) - it certainly does the job well for solar....

It's mounted on the HEQ5pro (why? because that's what's available!)

No issues, no drama.