Esprit 100 with flattener and ASI533MC-Pro

[PeterCPC]

I just got an ASI533MC-Pro after my ASI385MC-Cool packed up.

Anyone using this combination? I am interested to know what you have in the image train to enable focus. I tried a bit of daylight imaging and I needed the 21mm spacer to be able to get focus. This was on a fairly close object - will it be the same at night on astronomy targets?

Thanks in advance for any pointers.

Peter

[fireshipjohn]

The Skywatcher flatteners need 55mm of backfocus to achieve a flat field, this ZWO article may help in planning the layout.

https://astronomy-imaging-camera.com/tutorials/best-back-focus-length-solutions-55mm.html

I have an ED80 with the flattener and it all works fine, should be similar or better on an Esprit

[Adam J]

The camera has a 6.5mm backfocus without the black threaded adapter on the front, with it its about 16.5mm so you will need another 38.5mm between that and the m48 adaptor on the Esprit 100 flattner.

Adam

[PeterCPC]

Thank you both. So it looks like I keep the 11mm ring on the camera and add the 21mm and 16.5mm extenders.

Peter

Edited May 28, 2020 by PeterCPC

[Juicy6]

My setup, 57,3 mm + 6,5 mm = 63,8 mm, minus one third of filter thickness gives close to 63 mm.  The spacer/extender ring to the left of the flattener is 8 mm so distance from this ring to sensor will be 55 mm.

Christer, Sweden

Edited May 28, 2020 by Juicy6

[PeterCPC]

On 27/05/2020 at 19:03, Adam J said:

The camera has a 6.5mm backfocus without the black threaded adapter on the front, with it its about 16.5mm so you will need another 38.5mm between that and the m48 adaptor on the Esprit 100 flattner.

Adam

Adam

If I use a filter cell adapter before the flattener which is 9mm wide apparently (I couldn't see any other way of using a 2" filter) will this affect the back focus? My imaging train would be camera with 11mm adapter, 16.5mm and 21mm adapters, M48 adapter, flattener. filter cell adapter.

Peter

Edited June 3, 2020 by PeterCPC

[Juicy6]

2 hours ago, PeterCPC said:

Adam

If I use a filter cell adapter before the flattener which is 9mm wide apparently (I couldn't see any other way of using a 2" filter) will this affect the back focus? My imaging train would be camera with 11mm adapter, 16.5mm and 21mm adapters, M48 adapter, flattener. filter cell adapter.

Peter

No, distance from flattener to sensor remains the same. But you will have to move focuser draw tube inwards 9 mm. Or you can use a filter drawer...

[PeterCPC]

23 minutes ago, Juicy6 said:

No, distance from flattener to sensor remains the same. But you will have to move focuser draw tube inwards 9 mm. Or you can use a filter drawer...

Thanks. So the filter cell has no effect on back focus - great.

Peter

[prusling]

My experience is that accurate measurement of the resulting total backfocus is essential (e.g. with digital calipers) as sometimes spacers (for example) don't fully thread in so take up more space than expected...  Many times I've worked it out on paper then measured the result only to find it's out!

[PeterCPC]

Good to know - thanks.

Peter