Asahi Pentax Super Takumar SMC 200mm

[Thalestris24]

Yes indeed... fine for nebulae and diffuse objects, but won't it limit the magnitude of stars (point sources)?.... but I guess there will be enough of them in the wider field that 200mm gives.

Hi

Not really. I think sky conditions are more limiting. The lens is fixed focal length so a smaller aperture will require longer exposure time to get the same amount of data. Having said that, I probably wouldn't choose to image at f8 when it could be f5.6 or even f4. I'm not sure how well it might perform wide open - I'll have to try and see when I get some clear time. It is indeed mounted on my heq5 now and patiently waiting

Louise

[Thalestris24]

Hi all

Finally had a first light with the Takumar last night! I had planned to do some guided images but my finder guider wasn't playing ball with PHD2. I suspect the cable was picking up noise from nearby mains cables... Anyway, after much fiddling I eventually gave up the guiding idea and just did some unguided shots. By the time I'd got to doing them the Milky Way proper was out of reach and I took some images nearby - vB151 - a dark nebula, according to Stellarium. I took some 45s subs at F4 and eventually stacked 11 of them. However, even 45s subs were overexposed for the background... Next time I'll stop down to F5.6 but really I need another clip filter for the lp. Really I need darker skies!

Anyway here it is after minimal processing (edit: just lights stacked, no calibration frames):

And a crop of the central region:

What does anyone think of the lens performance?

Thanks

Louise

[kalasinman]

Looks like a keeper, Louise. Nice star shape and color. Really like it.

[Thalestris24]

Looks like a keeper, Louise. Nice star shape and color. Really like it.

Thanks - shame about the usual gradients The setup as is, is very unbalanced and I'll have to procure some weights to sort that out. The vintage Takumar is quite heavy. Hopefully I'll be able to do some better images in the future. Might get the camera modded too.

Louise

[Alien 13]

The image looks fine to me, the star bloat on the very brightest stars can be dealt with quite easily and there seems to be little or no coma so I would continue to use it wide open.

Alan

P.S did have a little play around with PS to get a good look hope you dont mind.

[kalasinman]

Hmm, modded? Veil, Heart, Soul, Rosette?

[Thalestris24]

Hmm, modded? Veil, Heart, Soul, Rosette?

Maybe! Later in the year perhaps... I find my other 1100d which is full-spectrum modded, is much more sensitive generally and not just in the red end of the spectrum.

Louise

[Thalestris24]

The image looks fine to me, the star bloat on the very brightest stars can be dealt with quite easily and there seems to be little or no coma so I would continue to use it wide open.

Alan

P.S did have a little play around with PS to get a good look hope you dont mind.

Thanks! I only did very basic processing - StarTools and some tweaks in paint.net. Some flats, at least, would help - when I get around to doing some! May I ask what you did in PS?

Louise

[Alien 13]

Thanks! I only did very basic processing - StarTools and some tweaks in paint.net. Some flats, at least, would help - when I get around to doing some! May I ask what you did in PS?

Louise

Hi Louise

I basically made an artificial flat by

Duplicating the image

Filter  noise dust and scratches to remove the stars (radius 40 threshold 10)

Filter blur gaussian blur about 20

Then i invert the image (the artificial flat) and using levels moved the 255 slider in slightly (this prevent the final image being clipped on the blacks)

I then use the colour burn blending mode and flatten the image

The tricky bit is getting the inverted image levels correct and making sure there are no other artifacts present (these can be paintbrushed out using the correct colour selected by the eyedropper tool)

Hope that helps

Alan

[Thalestris24]

Hi Louise

I basically made an artificial flat by

Duplicating the image

Filter  noise dust and scratches to remove the stars (radius 40 threshold 10)

Filter blur gaussian blur about 20

Then i invert the image (the artificial flat) and using levels moved the 255 slider in slightly (this prevent the final image being clipped on the blacks)

I then use the colour burn blending mode and flatten the image

The tricky bit is getting the inverted image levels correct and making sure there are no other artifacts present (these can be paintbrushed out using the correct colour selected by the eyedropper tool)

Hope that helps

Alan

Ah, ok - thanks. I'll make some proper flats - easy enough to do!