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Solar imaging - need to grasp the fundametals


nightvision
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Hi, I don't know anything about solar imaging (or observing) and would like to understand the fundamentals, I have noticed big price differences in the equipment, there seems to be several approaches. Is there a thread that covers the basics along with the potential results? Hopefully I can then decide where to best spend the money.

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To start yourself off with some simple white light imaging you could try this tutorial: http://stargazerslou...-solar-imaging/ (modesty forbids me from mentioning the author's name :p ) - total additional outlay about £20 for the filter (your ED100PRO would be ideal with your 300D). Then there is the more specialised Hydrogen Alpha solar scope like the Coronado PST at about £600. You can go on from there depending on the size of your wallet.

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It is important to distinguish two main directions: white light, and single-spectral-line imaging/observing. The latter is usually the H-alpha line, but the CaK line of calcium is also used. In both cases you need to reduce the amount of energy entering the eye or camera dramatically or else suffer the dire consequences. The difference is that in white light imaging, you reduce the energy at all wavelengths equally, obtaining an image of the photosphere of the sun, i.e., the layer emitting most of the light. An H-alpha or Ca-K scope removes all light entirely, except for a tiny transmission band, less than 0.1nm across (0.07nm in my LS35). In the case of H-alpha, this allows study of the chromosphere of the sun, the layer just outside the photosphere. This layer absorbs the H-alpha light from the photosphere (causing a dark absorption line in the spectrum), but emits part of it again at the same wavelength.

White light is simplest and cheapest: for al telescopes, simply put a solar filter (Baader Solar Film is favourite) and mount it in front of the scope. use any EP you like to view the sun. Note that although film or filters made for visual can in principle be used for imaging, special imaging film and filters let through more light and are not suitable for visual use without additional filters.

In refractors (alone!!) you can also use a Herschel wedge. This lets through most of the light, and only reflects a bit of light towards the EP or camera. Here too, additional filters are needed before the light is dim enough to view.

H-alpha and the like require very expensive kit. Using very special interferometric filters (so-called Fabry-Perot etalons), combined with energy rejection filters (ERFs) and a blocking filter at the rear, all wavelengths except the one you want are blocked and viewing/imaging is safe. As a comparison: a few tenners get you into white light, my second hand Lunt LS35 (35mm H-alpha scope) set me back 505 euro, which is a very good deal indeed. A 60mm H-alpha scope can quite easily be around 2000 euro.

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Hi,

I would second the comments from Roger and Michael, start with white light either by buying some Baader solar film and make a filter or buy a ready made one. FLO sell some nice ready made Baader solar filters that aren't too expensive. Your ED100 would be a great scope and either of your Canon cameras could be used for white light imaging. A lot of white light images use a Canon.

As for narrow band (Ha and CaK) I would leave those until you have had a go at white light. Prices start to get a bit high and it is always best to dip your toe in first.

Robin

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Thanks to everyone of the detailed information :cool:, I am certainly now in a position to make some informed choices. It seems (like many branches of this interest) that it could easily become a wallet draining experience, I will tread carefully.

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Another vote for Baader solar film on your ED100. That won't drain the wallet too much, it's one of the few bargains in astronomy! :)

Thanks to everyone of the detailed information :cool:, I am certainly now in a position to make some informed choices. It seems (like many branches of this interest) that it could easily become a wallet draining experience, I will tread carefully.

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'bargains in astronomy' I like the phrase, Luke. In fact with your permission I will use it on Mrs DrRobin next time I want a new telescope/mount/obs/gadget. Something like 'it was a bargain, it would have been criminal to leave that C14 in the shop the money they were asking for it.'

But seriously, Baader solar film is very good, it is strong, durable and performance is as good as anything costing several times the money. A filter is really easy to make with a bit of cardboard and some film.

Robin

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Thanks to everyone of the detailed information :cool:, I am certainly now in a position to make some informed choices. It seems (like many branches of this interest) that it could easily become a wallet draining experience, I will tread carefully.

Actually, I think it's fairly safe to say that most solar observers probably only spend a small fortune once and then stick. It's not like night time astronomy where there are so many different types of scopes, eyepieces, mounts, and the rest of it that all perform well on certain types of viewing or targets, so you might end up with two or three scopes on the go at once... with the sun there is only one target, you won't point your solar scope at anything else, so once you've got your Ultimate Solar Scope there's not much more to spend money on (unless you really must have Ha AND CaK).

It is true that one can spend thousands on a single solar scope or just a few hundred, but there is a reasonable amount of choice for different budgets, they tend to have big jumps in price though.

Edited by jonathan
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