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email dave@allmon.com
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Flat Test

 
secbaffleoff_before

The stock secondary baffle.
Snap011

This is a flat field frame shot before any modification to the scope. There are no filters installed.
secbaffleoff_after

A ring was made from 2mm foamie, slightly undersized. When it is stretched over the secondary baffle, the foamie distorts into a cone shape. It has a wider flare than the stock secondary baffle.
seethrough

Looking in the front, you can see clear through the scope. Off axis light can make it into the camera.
secbaffle_after

There is no longer a path through to the focal plane from the front.
flat_noextbaffle flat_extbaffle

The SCT adapter is baffled front and rear.


MAX: 984
MIN: 745
AVG: 894.505

Same as left, but an external baffle is added as shown in the photo below.

MAX: 632
MIN: 469
AVG: 575.299
flat_rearnoextbaffle flat_rearextbaffle

The rear SCT adapter baffle was moved to be behind the focal reducer.

MAX: 799
MIN: 547
AVG: 721

The rear SCT adapter baffle was moved to be behind the focal reducer and the external baffle was added.

MAX: 629
MIN: 410
AVG: 546.445
flat_focused flat_focusedext

This time I tried to focus on a card about 35 feet away from the scope. There was a plant 6" in front of it that I focused on.

MAX: 866
MIN: 639
AVG: 771.192

This time I focused on a card about 35 feet away from the scope and used the external baffle.

MAX: 514
MIN: 337
AVG: 442.626
external_baffle

The external baffle.

Ok, so all of this messing around hasnīt gotten me any closer to a flat field frame I can use to fix my images. So as a last effort, I placed a white posterboard on an easel at 37ī 5" from the front of the scope. On the posterboard I hung a sheet of graph paper. I focused on this paper and shot 10 frames. Then I removed the graph paper, still focused on the same spot and shot 10 more frames. These last 10 became my in focus flat field. Then I racked the focus out a bit - about 5 full turns on the focus knob - and shot 10 more. These last 10 are the out of focus flat field. I flat fielded the image by each flat field.
ffinfocus ffoutfocus

The in focus flat field frame was used on this image. The illumination was somewhat uneven, coming from a 45 W flood about 10 feet up and to the left, and pointing away from the card.

Same image frame, but using the out of focus flat field.