White Light Sun - 16th October

[markt]

Got the Lunt Solar wedge out today - lots going on so the perfect photo opportunity! Taken with the 70mm frac @ f12, Baader continuum filter, DMK31...

wl full disk by Mark Townley, on Flickr

[PeterW]

Stitched from how many frames?? Shows that full disk white light can actually be worthwhile! Lovely granulation, sometimes I find that stacking software has trouble tracking when the detail is not obvious, but yours looks crisp from edge to edge! Excellent! Is your scope an achromat, I am looking to get something a little bigger for white light and wondering if cheap is a valid option?

Cheers

PEterW

[spaceboy]

Great pic Mark. I braved it today for the first time in a while and was happy I did. I was amazed to see how much was going on and that one sun spot is HUGE.

[markt]

Thanks for the kind words both of you!

Peter - this is a mosaic of 6 panes. The scope is the IKI 70mm f6, at £244 I think it is an absolute bargain! I can use this aperture pretty much all of the time (for solar) tbh, regardless of seeing... There's often many an occassion when my 127mm frac is just too big for the seeing - i'm really tempted to get a 102mm f7 (IKI); I think I would get to use this on all but the worst days, and the extra aperture would pay dividends in the resolution department.

I think the key to getting granulation in WL imaging (at wide field scales) is to drop the gamma on the camera slightly from the default and to use a narrow band filter to help freeze the seeing. Normally i prefer to image in WL at 705nm - the longer the wavelength the less susceptible it is to the effects of poor seeing (& I have plenty of poor seeing!) - but a conventional nightime Ha filter at 656nm will work just aswell.

Is cheap a valid option? Yes, if you image at narrowband wavelengths and you have a good focuser on it...

HTH,

Mark

[PeterW]

I use a 66mm WO refractor, wedge, nd 1.8 (for very short exposures) and a 705nm filter, got surprising granulation a week or so ago. I sold my ST120 earlier in the year and am regretting it, just wondering how much more aperture it would be worth investing in. As for the IKI 102mm, do you mean the Ikarus model?? How much is it selling for? I was wondering about a 90mm f5.5 semi-apo from Teleskop service? I only use 10:1 dual speed crayfords now.... as you say getting precise focus especially when barlowed in is KEY, the ST120 had been upgraded in this way!

All the best

PEter

[markt]

I've thought of doing a bit of surgery on the wedge and replacing the stock ND filter for a 1.8, get the exposure time cut back as much as possible. Yeah, the 102 is the IKARUS model, think it's selling for about 600 quid ish. There's a few options in this size and at this price bracket...

[p1taylor]

Hi Mark, That is a really great image of detail.

peter

[PeterW]

I have the intes wedge... so the choice of filter is mine.... but then so it the (accidental) choice of frying my eyeballs.... One has to be VERY careful, cameras are not as fragile as eyeballs. With the nd1.8 I aim to keep the exposures well down the hundredths of a second.

Cheers

PEterW

[Montana]

All your full discs are 1st class Mark

Definitely change to a 1.8ND Mark if you can, you won't regret it. I changed to the 1.8ND alone on Saturday and it made a huge difference compared to the 2.4ND I had in before.

Alexandra

[Cschur]

Mark, once again a killer shot. Have you tried as you mention a comparison of a night time say 6nm Ha filter to the TiO? I have to try this too. I think my Hbeta filter is too blue to clean the seeing up.