Which of scopes these for solar use?

[StevieDvd]

I had been considering buying a good solar filter for my megrez 72 and have a bash as some basic solar imaging. But came across a few people who use their Nexstar 4SE for solar work.

As I have one of these sitting unused in the garage perhaps that would be a better bet.

So megrez 72 or 4SE?

Obviously will need the filter but anything else such as 1.25" filters?

For obvious safety reasons I don't think I'll be making the filter. Will look to get a proper end cap type one for the scope I end up using. So any suggestions there welcome too.

Thanks

Steve

[Ags]

I have a 4SE too so I am interested in this topic too.

Steve, you also mention filters... I've been wondering about this too. Could you combine a white light filter on the front of the scope with a Ha eyepiece filter to view granulation and prominences?

[John]

Aperture is always good so I'd say the 4SE. Get a full aperture filter such as a Kendrick or similar and you are good to go

[StevieDvd]

Thanks it looks like the 4se has had a short stay of execution then!

With the goto function it will also track the sun -or rather adjust for the earth rotation.

Off to google the suppliers now, if I order tomorrow and don't get next day delivery we'll be in for a sunny weekend.

[Merlin66]

The larger aperture would be better.

No, you can't just add a secondary filter to a white light system to view the filaments and proms - you need a specialised Ha etalon filter ie Coronado/ Solarview/ Lunt.

A light green or Baader Continuum filter on a white light system will however improve the constrast.

[markt]

Sorry to go against the grain here guys - but i'd go for the 72mm megrez. A frac is always going to have more image contrast, plus ultimately you can use a solar wedge with it. Don't know if the 4se has a slow motion focuser, but I think the megrez does, and with this you will find focusing much easier. Why not buy a sheet of baader film and try both out? You should be able to make a filter for both with an A4 sheet.

[Ags]

Merlin66, I don't doubt what you say - but I am surprised that filtering for Ha light is not sufficient to view solar details. Can you explain why? What does the etalon do exactly?

[StevieDvd]

I went for a Thousand Oak filter for the Megrez to start with as that's one scope I'm sure I'll be hanging on to for some time (suffice to say I call it 'my precious' as I like it so much). Although a lot more expensive than a diy baader film one I wanted something safe and durable.

To say I err on the safe side is possibly an understatement - the filter cap was a loose fit and I wanted no chance for it to get knocked off by accident so I used a heap of electricians tape to hold it in place as well. Could not risk harming my eyes or the innards of the megrez. I'm pondering on several options to hold the filter in place safely without using sticky tape - will update when I find a nice elegant solution.

Once I was sure it was safe I cycled through a few eyepieces from 25mm down to 5mm and just had a small yellow circle on a black background - nothing special to see and my daughter was most unimpressed.

Did not manage to get the focussing sorted but took a few pictures on a DSLR - still just plain yellow circles. I'll load them onto the PC later to see if there is anything hidden that a few tweaks may bring out.

I've yet to try with a webcam or video camera yet so haven't given up getting something worthy of posting.

Still early days and hopefully a few sunny ones yet to come.

[MjrTom]

Sorry if this is too off topic but how do you go about adding a HA filter to a Megrez 72 or any refractor in this aperture range. (My ED80)

Seen images using a 50mm lunt HA front filter but no idea how this is achieved.

[Merlin66]

Ags/ MrjTom,

To view the Sun in all its Hydrogen glory, you need to be able to view it in the light of Hydrogen alpha. This is an extremely narrow bandwidth - only 0.07nm wide. If the filter has a bandwidth greater than this ie the DSO Ha filters etc etc then you cannot see the Ha detail.

To achieve this very fine tolerance, and be able to view it safely most Ha solar telescopes use a combination of two filter elements:

The etalon filter which provides a series of images every 9-10A centred on the Ha. This can be mounted in front of any telescope (SM40/SM60 and Lunt front filters) or in the case of the smaller PST and Lunts a smaller sub-diameter etalon is used.

The next filter usually placed close to the eyepiece is the blocking filter. This sorts the "comb" of bandwidths passed by the etalon and only allows the Ha to get through.

These two filters must ALWAYS be used as a pair - that's how they work.

Adding any filter behind a white light solar filter (ie Baader) will NEVER show the Ha detail - some filters like the Continuum do increase the contrast on white light surface details.

HTH

[MjrTom]

Thanks for the clarification

[markt]

I would use your webcam for images in WL if I was you, IMHO decent solar shots taken with a DSLR are very few and far between. How much of a gap do you have between the OTA and the filter cell?