Comments

Hi Ken,

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I was simply amazed by your published before and after photos, and how to use a telescope from a building.  It must not have been easy there in the icy lands.  I admire your work and thankfully there are people like you explaining everything.   Great success to you and I hope it will continue for a long time to come.

Ivan,

Brazil

November 10, 2020

Hi Ken,

Thanks for sharing your experience and practical advice. I have a very similar setup with an 8SE and Skytravel 102. Ive been trying to use a cheap generic 0.5X focal reducer but am having problems with severe off axis aberrations on the 8SE. What brand of focal reducer are you using, and how do you set it up in the optical path?

Thanks Michael

August 23, 2021

Hi Michael,

Focal Reducer

My FR is inexpensive, a 0.5x from Antares for about $30.

I had three problems with it.  Here’s how I fixed them (I can’t remember the exact details)…

1. Placement in the optical path regulates the power of the FR.  The farther away from the CCD sensor the stronger the reducing power.  I placed mine as far as I could from the sensor, at the end of the tailpiece that’s goes into the visual back.  This yielded 0.56x, the max I could get.  You can measure this by measuring the FOV of the photos with and w/o the FR in place.

2. The other problem was like yours, aberration.  I also had ghosting.  Not sure what I did here but I experimented with placement…, removing the lenses from the barrel and putting them in backwards and or reversing the lens order within its barrel.  This took me some time but it did work for me.  

3. Bloated stars. This was remedied by using a IR/UV cut-off filter (also about $30).

My images now have no aberration or bloating but I sometimes have ghosting on a bright star and I’m working close to 0.5x on the FR.

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Ken