Advice on viewing with Lunt Herschel Wedge

[RobertI]

I have a Lunt Herschel Wedge arriving in the next couple of weeks and I am planning to use this with my WO 66mm refractor and my highest mag 5mm eyepiece. I believe the FOV will be roughly as shown below, ie: full solar disc. I am completely new to solar observing but the plan is for visual initially and then some imaging with my Canon EOS.

I realise my question may be a bit premature given that I haven’t got the Wedge yet, but should I plan for some higher power viewing too, or will full disc viewing keep me busy for a few months? If higher power, what would be the best way to go; a barlow,  a shorter FL eyepiece or a cheapish long FL achro refractor??

Any thoughts appreciated.

Rob

[hunterknox]

Solar's a different kettle of fish when it comes to magnification. I can rarely use magnification over about 60x because the seeing's so affected by the sun's warming effect and I don't think that's uncommon.

See how you get on with your existing eyepieces, figure out what your optimal magnification is and if you do feel the need to change try a simple eyepiece like a plossl or an orthoscopic - fewer glass elements is usually better, in my experience.

[spaceboy]

I agree with above. I'm not a big fan of magnification on the sun and prefer to stick to around x33. I know many others push the mag up to x60 and beyond but I have never found this much fun and soon gives me a headache. There was the one time when I managed x96 and the views were mind blowing but that was in a 5" refractor and the seeing was perfect.

[RobertI]

Thanks for the responses, I'm glad I asked, the heating effect of the sun on the image quality is not something I had considered, seems obvious now! Sounds like the 10mm e/p giving 40x will probably give the best results but I shall experiment with what I have.

Rob

[Pig]

My preference differs from the above when using a Hershel wedge

I use a 6mm 50 degree FOV eyepiece giving 83 x magnification and I see just over a full disc view. The detail on the spots and their surroundings area are excellent in white light using the HW, although lower powers do aid with bringing the granulation out. I also use the 4mm in the summer months with no loss of detail and on the super seeing days the 2.5mm comes out.

As hunter says, experiment with the eyepieces you have to find what suits you best.....

[Moonshane]

I think the 40-70x range is most common and more than enough to see everything available.

[LukeSkywatcher]

Not that i should be dishing out advice about the wedge because ive only got mine a couple of weeks and not really used it yet. I am just wondering if you have all the correct filters for use with the wedge: ND3.0, Polarising filter and maybe a solar continuum filter?.

I only ask because i see no mention of them in your original post.

[RobertI]

Not that i should be dishing out advice about the wedge because ive only got mine a couple of weeks and not really used it yet. I am just wondering if you have all the correct filters for use with the wedge: ND3.0, Polarising filter and maybe a solar continuum filter?.

I only ask because i see no mention of them in your original post.

Thanks for asking Paul, yes i have a polarising filter, and the wedge comes with a built in ND3.0 filter (i will double check this though). And the Baader Continuum filter was going to be next on my list once i've had an initial play with it.

Let me know how you get on with yours.

Rob

[Luke]

For me, it's normally 72x mag with my 60mm grab and go scope and Herschel wedge. With my ED100, 112.5x, or if I want to sneak in closer and conditions are okay, 180x.

I try to observe when the seeing is typically better, this will vary from place to place and can change during the year.

For me at home, it's normally mornings that are best and lunch time that's worst, but it can vary, I have now and again had very good views around lunch time.

[LukeSkywatcher]

For me, it's normally 72x mag with my 60mm grab and go scope and Herschel wedge. With my ED100, 112.5x, or if I want to sneak in closer and conditions are okay, 180x.

I try to observe when the seeing is typically better, this will vary from place to place and can change during the year.

For me at home, it's normally mornings that are best and lunch time that's worst, but it can vary, I have now and again had very good views around lunch time.

This raises a good question which i was going to ask. I may as well ask here and now.

We know that at night when observing, the best views are gotten when objects are at their highest point in the sky (zenith). This is because they are directly overhead or close to and the light from the objects is more direct and focused because there is less pollution to scatter the light and the angle involved helps etc. So.............in the same way, i am guessing that the best time of day to observe the Sun is when it is at its highest point (midday) and an hour or two either side of. In the morning and evening there is too much pollution in the atmosphere for best viewing results?. 

Then again, i know the light from the Sun is so much more then viewing other stars at night which are so much further away from us. Maybe the same rules dont apply for the Sun because it is so close?.

[hunterknox]

...in the same way, i am guessing that the best time of day to observe the Sun is when it is at its highest point (midday) and an hour or two either side of. In the morning and evening there is too much pollution in the atmosphere for best viewing results?. 

Then again, i know the light from the Sun is so much more then viewing other stars at night which are so much further away from us. Maybe the same rules dont apply for the Sun because it is so close?.

It all comes down to seeing again. You're right that you get the same peering-through-the-atmosphere effect when the sun's very low down but it's usually dominated by ground effects once the sun's heat kicks in and that's worst around mid-day. That's why a lot of land-based solar observatories are up towers and by lakes - it's the best way of ensuring a stable atmosphere.

I also find the seeing effects to be wavelength dependent, which would make sense given that red light is refracted to a lesser degree than blue. Back when I was doing imaging I tried to get calcium K done before 9:30, white light before 10:30 and H alpha shortly after. In winter it can be better for observing in some ways due to the lack of a significant temperature differential.

One of the best tips I've picked up for white light is that if you switch a continuum filter for a red filter when the atmosphere gets choppy you can get a better view until the seeing breaks up altogether.

[LukeSkywatcher]

It all comes down to seeing again. You're right that you get the same peering-through-the-atmosphere effect when the sun's very low down but it's usually dominated by ground effects once the sun's heat kicks in and that's worst around mid-day. That's why a lot of land-based solar observatories are up towers and by lakes - it's the best way of ensuring a stable atmosphere.

I also find the seeing effects to be wavelength dependent, which would make sense given that red light is refracted to a lesser degree than blue. Back when I was doing imaging I tried to get calcium K done before 9:30, white light before 10:30 and H alpha shortly after. In winter it can be better for observing in some ways due to the lack of a significant temperature differential.

One of the best tips I've picked up for white light is that if you switch a continuum filter for a red filter when the atmosphere gets choppy you can get a better view until the seeing breaks up altogether.

So as i suspected (but had to ask), the same rules do not apply for solar observing because as you say the max heat and atmospheric turbulance are greater around the time the sun is at it highest.

Regarding continuum filters. I did buy one but suspect i may not get too much use from it. I did have a full set of coloured filters a few yrs back but gave them away. Times (and my gear) have changed since then and i'm thinking i may need to buy a new set of them. Not just for solar viewing, but for dragging out details on planets also........now i have a scope worthy of their use (8" SCT).

[LukeSkywatcher]

I found them (coloured filters). They are from the same place i bought my wedge and solar filters. I'm in no rush for these and have a birthday coming up in 4 weeks. Think i'll let the mammy buy these for me as a gift.

http://www.astroshop.eu/omegon-color-filter-set-1-25-6-pieces-/p,11333

[Qualia]

In the TV 76 f6.3 with a Lunt Herschel Wedge, I find a 9mm B.G Ortho my most used eyepiece. It offers 53x magnification and an ample 0.7º true field of view. If seeing is good and I want to hone in on a little detail, I might up the power to a general maximum of 80x.

It's very much the same story with the Tal 4" f10 but with different eyepieces. The most used eyepiece in that scope is the 19mm Panoptic, giving about 53x and 1.2º true field of view.

Curiously, and I say this just in passing, I don't get along well with the 10mm or 14mm Delos for white light. I don't know why, but I much prefer the little Orthos. Either way, the smaller 3" doesn't give anything away to the 4" in terms of resolution, contrast, quality of detail and so on.

For general Wedge usage I use the necessary ND 3.0 filter, a variable polariser and continuum filter from Baader. For a good while I simply used a blue and yellow filter to get that continuum green look (until a proper filter turned up secondhand) and from time to time a red filter to enhance detail in the umbrae.

Nevertheless, the best views I've obtained is with the three standard filters. When seeing is good, a lot of detail can be tweaked in white light. You will be able to detect subtle differences in tone in some umbrae - a kind of very deep dark brown, you'll be able to identify pores, light bridges and subtle streaking within the penumbrae. Faculae will also be very prominent and generally suggests the promise of new activity in the next day or so.

Here's a sketch picked at random to show what is generally observed at the eyepiece, taking into account that the live image is infinitely better:

[RobertI]

Thanks for the further comments folks. Fortunately i recently acquired a set of coloured filters so may try these to improve the experience. Sounds like my setup should be fine to get me started......