I was considering taking photos of the moon and stumbled on a review of the MTO 1000a mirror lens. This is acording to this site a sovjet design from the eighties of an 1000mm mirror lens. (Some other sources say 1100mm)


I was considering using this with an x2 teleconverter to take pictures of the moon.

Considering the bad reputation mirror lenses have, would I get better results using the Sigma 150-600mm contemporary lens along with 2 x2 teleconverters?

  • 1
    \$\begingroup\$ Which teleconverter(s) are you talking about? They all perform differently. \$\endgroup\$
    – scottbb
    Commented Jan 22, 2018 at 3:30
  • \$\begingroup\$ Why would you want to use TWO 2x teleconverters on a Sigma 150-600 lens. Using ONE 2x would give you 1200mm. Do you really want 2400mm? \$\endgroup\$ Commented Jan 22, 2018 at 13:45
  • \$\begingroup\$ I was aiming for 1800mm or more. If that is a good idea remains to be seen. \$\endgroup\$
    – lijat
    Commented Jan 22, 2018 at 14:38
  • \$\begingroup\$ i think you should rephrase question to be something like: "I want to take photographs of X (moon, bird 200km away, sports person - be detailed). I own this equipment: a,b,c,d,e. Will that be enough? Would buying Z,Y,W help? what is missing?" Right now people are trying to solve problem they don't understand, help them! \$\endgroup\$ Commented Jan 23, 2018 at 3:08
  • 2
    \$\begingroup\$ We understand the problem: Someone wants 1800mm+ focal length without spending $10K+. \$\endgroup\$
    – Michael C
    Commented Jan 23, 2018 at 4:31

2 Answers 2


Teleconverters and lenses tend to have to be somewhat matched to work well. I'd be very surprised if two TCs, aside from giving you a very dark f/25 lens, would give good results; it's simply not a scenario the lens designers had in mind.

If you really, really want that sort of reach for astrophotography (which I admit is beyond my experience) then I'd suggest you're better off getting a smaller sensor camera such as a micro four thirds, and an adaptor to mount it on a telescope.


The mirror lens is f/10 (and M42 screw mount), the Sigma is going to be f/6.3 - double that for each 2x TC.

Mitch reports his experience using a 1325mm telescope (on an APS-C sensor): the frame is filled, the moon moves out of frame in 10 seconds, and the result is soft; so you want a fast shutter.

The mirror alone will be brighter and likely not as sharp as the Sigma with a quality Teleconverter, which is expected to be sharper but darker.

The mirror has one focal length while the TC will fit all your lenses (doubling your portfolio). I know what I'd buy (the TC) but the mirror is low cost (plus adapter, assuming you don't have an M42 screw mount camera).

With 2 TCs you'll need an equatorial mount to race the moon and keep the shutter open.

It's a question of how many photos of the moon you want and how good you want them to be, for how much money; you can download $1M photos of the moon for free.

If you want photos of all the planets and stars a telescope with a computerized mount will set you back about a thou (depending upon what you want). Enjoy downloading from 10's of thousands of websites while you decide how much time and money to invest, and for what result.


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