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iwols

skywatcher 0.85 flattener on ed80?

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hi all just wondered if anyone had comments or examples on what this does exactly thanks

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If you are using a larger sensor camera (such as a DSLR) it will be critical to get you a flat field and therefore nice round stars at the corners. Also the added benefit is that your telescope speed will increase by 0.85x and the size of your field of view will appear larger too.

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Basically a fieldflattener is only used for AP. Is that your intended use?

If so, you have to decide on the sensor type you are going to use. Webcams for planetary AP have only a very small sensor and mostly do not need a fieldflattener. On top of that the loss of focal lenght is a disadvantage. Better use a PowerMate or good barlow for that purpose

If you want to go for deepsky imaging and use a DSLR or CCD camera you need a wider and flatter field. APSc size camera's like most DSLRs need at least a 25 mm flat field, while the larger sizes need an accordingly larger flatfield. The specs of a decent field flattener will tell you the obtained flatfieldsize. In the case of deepsky imaging the faster speed of the scope with the ff is desirable, but only if you want to go for the larger objects. If you want to go for smaller objects like galaxies, again the loss of focal lenght is a disadvantage.

So... the € 10,000 question is:  What is your intended use? 

Regards,

Waldemar

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thanks mainly dslr and dso cheers

That means the falttener will help you to get better results:  flatter field and wider vieuw for the larger DSOs

Be aware of the back focus distance of the fieldflattener: 55 mm. Your camera (Canon?) has a backfocus distance of 44 mm, so you need  a M-48 to Canon bajonet adapter on your camera for the M-48 thread on the field flattener and you will be ok.

Succes!

Waldemar

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I added a dedicated Skywatcher 0.85 Focal reducer/field flattener to my Orion (Skywatcher) 80ED and noticed a substantial improvement in image quality when shooting with a Canon APS-C chipped DSLR. - A good investment.  Getting the dedicated T-adaptor to connect the camera to the focal reducer also ensures a nice firm connection between the two and ensures that the focal reducer to imaging chip distance is smack on.

http://www.firstlightoptics.com/adapters/skywatcher-dslr-m48-ring-adapter.html

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Yes, field-flatteners/reducers are great!  On my TEC140 I use a 27TVPH from Astro Physics, because of 0.75 reducing factor I like that one better than the original TEC FF140 field-flattener which is not a reducer.

Waldemar

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Hi All - I have recently picked up the SW ED80, alas clouds have prevented me really using it but I cannot wait.

With regards to the field-flattener/reducer - I have no doubt it is a great bit of kit and will be on my list. I was wondering if any of you fine folks have a comparison image say of the same target, one with and one without the reducer on the ED80?

Cheers

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46 minutes ago, AstroKane said:

Hi All - I have recently picked up the SW ED80, alas clouds have prevented me really using it but I cannot wait.

With regards to the field-flattener/reducer - I have no doubt it is a great bit of kit and will be on my list. I was wondering if any of you fine folks have a comparison image say of the same target, one with and one without the reducer on the ED80?

Cheers

I have a SW ED80 and took a few subs last night. I can attach one later, taken without a flattener, using a DSLR and there is a fair old bit of coma.  I'm pretty sure I'll buy a flattener soon enough. 

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Yeah that would be great - I also use a DSLR.

I will most def be getting the flattener, but as the scope is so new I like to see what the difference my money is getting!

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Be aware that the distance between the flattener and the sensor should be ± 55 mm, but it may vary a bit. To get optimum results a little trial and error is necessary. The best to use for that is a set of shims like Baader's: http://www.baader-planetarium.com/de/zubehoer/adapter-foto-zubehoer/astro-t-2-system/t-2-abstimmringe-(set-mit-15-stück).html  For M48 aluminum or steel ones are available at AstrMarket. https://www.astromarket.org/accessoires-6/adapters-6/extension-2-6/t2-fine-tuning-ring---2mm817202-6  They got thinner ones as well.

Edited by Waldemar
addition

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5 hours ago, tooth_dr said:

I have a SW ED80 and took a few subs last night. I can attach one later, taken without a flattener, using a DSLR and there is a fair old bit of coma.  I'm pretty sure I'll buy a flattener soon enough. 

Generally, what appears to be coma in a refractor image is actually unfocused stars due to the curved field.  Field flatteners don't correct coma and refractors don't generally have any appreciable amount to correct anyway.

Field flatteners aren't just for imaging.  I use the TSFLAT2 flattener ahead of my 2" diagonal with proper spacing such that my AT72ED has a basically flat field at the shoulder of the 2" diagonal's eyepiece holder which is where most of my eyepieces' field stops are located.  It makes a huge difference when using widest field eyepieces.  Stars are pinpoint edge to edge.

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2 hours ago, Louis D said:

Generally, what appears to be coma in a refractor image is actually unfocused stars due to the curved field.  Field flatteners don't correct coma and refractors don't generally have any appreciable amount to correct anyway.

Ha well you learn something new everyday! It's the Newts that have the coma then! Thanks for explaining it 👍🏻

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6 hours ago, AstroKane said:

Yeah that would be great - I also use a DSLR.

I will most def be getting the flattener, but as the scope is so new I like to see what the difference my money is getting!

 

A few taken on Saturday night with an ED80 and 1000d DSLR, most are 300s subs.  I dont have a FF yet, and I think it would be a nice addition, plus a little bit more FOV would help squeeze in the targets better.

 

 

 

IMG_0014.JPG

IMG_0066.JPG

Edited by tooth_dr

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4 hours ago, tooth_dr said:

A few taken on Saturday night with an ED80 and 1000d DSLR, most are 300s subs.  I dont have a FF yet, and I think it would be a nice addition, plus a little bit more FOV would help squeeze in the targets better.

I hope you don't mind, but I did a quick edit to see how much detail was actually captured.  Quite a bit it turns out.

M31_edited.thumb.jpg.710ecb8e9657f396dbbe026c8fe3c118.jpg

M45_edited.thumb.jpg.328576b2be23af01f38d361ffd8fbd3e.jpg

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