[Mutley365]

Just bought my first mirror lens and managed to pick up a Tamron 55B SP 500mm, looking forward to posting some images, I enjoy astrophotography so I will most likely post lunar shots. I'll be interested to see what I can do with my o-gps1 unit that I have mounted to my K-5. I'll test it with my 2x tele-converter too, although I'm not that optimistic to be honest. Also it'll be interesting to see how it compares to my Sigma 135-400mm APO 400mm lens. Might be worth shooting some comparison shots with and without the 2x tele-converter.

[Jean Poitiers]

Just bought my first mirror lens and managed to pick up a Tamron 55B SP 500mm, looking forward to posting some images, I enjoy astrophotography so I will most likely post lunar shots. I'll be interested to see what I can do with my o-gps1 unit that I have mounted to my K-5. I'll test it with my 2x tele-converter too, although I'm not that optimistic to be honest. Also it'll be interesting to see how it compares to my Sigma 135-400mm APO 400mm lens. Might be worth shooting some comparison shots with and without the 2x tele-converter.

Congrats on your mirror acquisition ... it's a well thought of Adaptall-2 ... and in case you haven't seen this : https://www.pentaxforums.com/forums/lens-clubs/59769-adaptall-mount-club-tamron.html - J

[Mutley365]

Cool, I've just bought a Tamron adaptall-2 2x tele-converter 01F as well, so it will be interesting to see the reach that I will get. Good job I have a very sturdy tripod!

[Miserere]

Just bought my first mirror lens and managed to pick up a Tamron 55B SP 500mm, looking forward to posting some images, I enjoy astrophotography so I will most likely post lunar shots. I'll be interested to see what I can do with my o-gps1 unit that I have mounted to my K-5. I'll test it with my 2x tele-converter too, although I'm not that optimistic to be honest. Also it'll be interesting to see how it compares to my Sigma 135-400mm APO 400mm lens. Might be worth shooting some comparison shots with and without the 2x tele-converter.

If I were a betting man, I'd bet that your Sigma @ 400mm, slightly cropped to give a 500mm FoV, will beat out the Tamron mirror lens in contrast and resolution by quite a bit. We don't use mirror lenses for their sharpness or high contrast

[Mutley365]

If I were a betting man, I'd bet that your Sigma @ 400mm, slightly cropped to give a 500mm FoV, will beat out the Tamron mirror lens in contrast and resolution by quite a bit. We don't use mirror lenses for their sharpness or high contrast

Well, it will be fun to find out. From some of the mirror lens pictures I've seen some look pretty sharp. Also I always shoot in raw format and I'm pretty good at photoshop ha ha! I've just bought an adaptall 2x tele-converter 01f, so it will be an interesting comparison, as well as stir up some healthy debate.

[Miserere]

Well, it will be fun to find out. From some of the mirror lens pictures I've seen some look pretty sharp. Also I always shoot in raw format and I'm pretty good at photoshop ha ha! I've just bought an adaptall 2x tele-converter 01f, so it will be an interesting comparison, as well as stir up some healthy debate.

By all means, make some comparison shots and post them here for us to enjoy. At web sizing there shouldn't be much difference if you nail the focus, but at 100% is where you'll see the difference. I suspect that up to 8x12 prints there won't be much if any difference either.

As for the teleconverter, I've not had success with them in conjunction with a mirror lens. I've tried both the well-liked Tamron 1.4x and the Pentax 1.7x AF TC, none of which delivered good results. I'll be interested in seeing what you get with your Tamron adaptall TC.

[Mutley365]

By all means, make some comparison shots and post them here for us to enjoy. At web sizing there shouldn't be much difference if you nail the focus, but at 100% is where you'll see the difference. I suspect that up to 8x12 prints there won't be much if any difference either.

As for the teleconverter, I've not had success with them in conjunction with a mirror lens. I've tried both the well-liked Tamron 1.4x and the Pentax 1.7x AF TC, none of which delivered good results. I'll be interested in seeing what you get with your Tamron adaptall TC.

I haven't had much joy with tc's in the past either and my vivitar 2x tc is useful as a paperweight, although I seem to get ok results with it connected to my sigma 135-400mm apo. I read good things about the adaptall 2x tc and seen some awesome results with it on adaptall lenses and on mirror lenses too. I'll be boring my wife to death with it I'm sure next week.

[Miserere]

I haven't had much joy with tc's in the past either ...

I just wanted to make clear that the Tamron 1.4x TC and Pentax 1.7x AF TC are both excellent and I've got great results with them on a number of lenses...just not mirror lenses.

I've had no luck with a number of 2x TC's I've tried, so I gave up on them long ago. I never tried any of the Pentax-A 2x TC's, which some people report getting good results with; I was just never so desperate that I was willing to pay the asking prices.

[Stone G.]

I just wanted to make clear that the Tamron 1.4x TC and Pentax 1.7x AF TC are both excellent and I've got great results with them on a number of lenses...just not mirror lenses.

I've had no luck with a number of 2x TC's I've tried, so I gave up on them long ago. I never tried any of the Pentax-A 2x TC's, which some people report getting good results with; I was just never so desperate that I was willing to pay the asking prices.

Well, how about stacking two(!) Tamron Adaptall-2 01F teleconverters behind a Tamron SP 350mm f/5.6 Model 06B lens:


(click on picture to see larger image)

It actually did work for me:


(click on picture to see larger image)

Obviously, an image like this takes some stacking (8 images stacked in Registax) but where I shoot from - under an urban sky - stacking is a must no matter what lens I use because of poor seeing.

[ChopperCharles]

Stacking? What does that do exactly?

Charle.s

[Mutley365]

Stacking? What does that do exactly?

Charle.s

I use DeepSkyStacker - Free it's free to download. Basically it improves the picture quality. This sight will explain it better: How Image Stacking Works . Most good astrophotography including star constellations, nebulas, planets and of course our moon will have been stacked. Even the data from the hubble telescope gets the images stacked, a good example is the deep universe image that showed galaxies towards the outer reaches of the universe.

[Miserere]

Well, how about stacking two(!) Tamron Adaptall-2 01F teleconverters behind a Tamron SP 350mm f/5.6 Model 06B lens:


(click on picture to see larger image)

It actually did work for me:


(click on picture to see larger image)

Obviously, an image like this takes some stacking (8 images stacked in Registax) but where I shoot from - under an urban sky - stacking is a must no matter what lens I use because of poor seeing.

That's pretty good! Any chance we can see a 100% crop...?

How do you hold that rig steady? Do you use two tripods?

[ChopperCharles]

I understand how stacking works for celestial objects... but the moon is big and bright. Why stack for that?

Charles.

[Mutley365]

I understand how stacking works for celestial objects... but the moon is big and bright. Why stack for that?

Charles.

You would stack lunar images depending upon the atmospheric conditions, you may get a great shot in one image, but it would be many times better if you took several shots and stacked them, I have seen tonnes of moon pictures, you can bet that most of the decent ones are stacked. The atmosphere can disrupt your ability to get a sharp picture for different reasons, for instance at night heat radiates from the ground into the atmosphere causing distortion, also pollution plays a part too. Generally speaking the colder the better, especially for mirror lenses.

[Stone G.]

That's pretty good! Any chance we can see a 100% crop...?

How do you hold that rig steady? Do you use two tripods?

Sure, these are 100% crops:







The good thing about mirror lenses is their low weight - so, I only used one tripod for these images.

On consulting my notes, I see that the stack was based upon 8 images at 1/6 sec and 10 images at 1/16 sec