Meade ACF optics and focal reducers

[tonybarry (Tony)]

Hello people,

The Meade SCT scopes have two focal reducers made by Meade to reduce the focal length - the f/6.3 reducer and the f/3.3 reducer.

Both reducers apparently reduce distortion at the periphery of the image when used on the standard SCT. That is, to my ignorant mind, they act as field flatteners.

My question is; do these reducers also work correctly on the ACF optics, since the field is supposed to be flat out to the periphery already? Or do they introduce too much flatness (i.e. curvature in the other direction) and bugger up a previously flat field?

If they do bugger the ACF field, what methods are available to reduce the focal lengths of Meade ACF SCT scopes?

I have looked for these answers on other sites but have not found an unequivocal answer.

Regards,
Tony Barry

[marki]

Astrophysics CCDT67 works. Cheap to buy but a pain in the behind to get hold of. Not because they are rare but due to the dealers giving you the run around. This is a reducer only and at 0.67 will produce a 30mm fully illuminated imaging circle.

Mark

[citivolus (Ric)]

I concur on the AP CCDT67 being a pain to get your hands on. It took me several dealers before I found someone who would ship me one. One prominent US AP dealer told me outright that they could sell me one and could ship overseas, but that they had no interest as I was unlikely to be a future buyer from them so it wasn't worth their time...

[Benny L (Ben)]

Originally Posted by citivolus

I concur on the AP CCDT67 being a pain to get your hands on. It took me several dealers before I found someone who would ship me one. One prominent US AP dealer told me outright that they could sell me one and could ship overseas, but that they had no interest as I was unlikely to be a future buyer from them so it wasn't worth their time...

If thats the way they treat customers then i'd have no problems becoming someone else's 'future customer'

[rat156]

Why don't you go straight to the source. I buy all my AP stuff from AP. They are happy to ship OS and do so at reasonable rates, not the "we only ship with DHL" types which will cost you an arm and a leg.

Cheers
Stuart

[marki]

The problem I had Stuart was that they would not accept my credit card or paypal insisting on pay by wire as they led me to believe they could not process overseas CC. When I did this it cost me $40 dollars this side, and initially $35 stateside to transfer the money. When the money got there (amount in US dollars as quoted) the shop found their bank had taken another $25 US. It seems that this then magically allowed them to draw from my credit card (but we can't they said) then took another $25 US All up $100 US in bank fees to secure a $148 part. I wish OPT sold AP parts as they are a whole lot better to deal with then this mob and I certainly won't be using them again even if it means I never buy another AP product. When I have been to the AP site they also claim not to be able to accept foriegn credit cards or paypal also insisting on wire transfers. Is this a bluff or do they flex a little?

Mark

[Bassnut (Fred)]

Originally Posted by rat156

Why don't you go straight to the source. I buy all my AP stuff from AP. They are happy to ship OS and do so at reasonable rates, not the "we only ship with DHL" types which will cost you an arm and a leg.

Cheers
Stuart

Exactly, AP are easy to deal with, why bother any other way?. I used a 0.67 FR on a Meade ACF, works a treat.

Cant remember how I paid, but it wasnt a problem.

[DavidTrap (David)]

AP have happily taken large sums of money from me via CC. Just filled in an order form (including the 3 digit security code) and faxed it to them.

DT

[citivolus (Ric)]

Originally Posted by Benny L

If thats the way they treat customers then i'd have no problems becoming someone else's 'future customer'

Yes, I think it is safe to say that I will never buy anything from that company. I have purchased from the other US AP dealer in the past without issue, although I lived in California at the time and I don't think that Anacortes ships overseas, so they were not an option in this case.

In the case of AP, I ended up going straight to the source and they were pleasant enough to deal with.

[PeterM]

Hi Tony,
While this doesn't answer all your questions I hope it is helpful. I had received advice (from Optec) sometime ago that using a corrector/reducer combo in the ACF was not ideal.

You could consider the Optec F7 reducer (see link below). These are designed to work with refractors and do work very well with the Meade ACF (I use one on my 12inch LX200R). They are available at Sirius Optics (yes I declare I work there) for $369. If using with a camera/ccd you will also need a mounting plate to suit and these are around $85.
http://www.optecinc.com/astronomy/nextgen.htm

Peterm.

[M_Lewis (Mark)]

I found this out when I lived in the USA for a few years back in the 90s, owning an aussie credit card. Reason many business's in the states can't accept overseas cc's, is the post code (or zip code as they call it). Their system, takes 5 digits (not 4 like ours) and is required for processing approval. The not-so-obvious way to get around this - get an american express cc if you're dealing with american companies who can't get around this problem. Having said that companies such as OPT are excellent to deal with and accept all types of payment these days, so the system is improving.

[DavidTrap (David)]

I'm interested in this subject as there is little information about this on the web?

The AP corrector claims a 30mm illuminated circle with an distance from the reducer to the imaging plane of ~79mm. Reducing this distance will reduce the correction factor and increase the size of the illuminated circle.

The following are quotes from the AP website:

"To give a real world example, let’s assume the following: We will set up a system with the CCDT67 @ 16 mm; our AP16T - 2”/T2 nosepiece @ 29 mm; a color filter wheel @ 25 mm; and a CCD camera @ 25 mm. 16+29+25+25 = 95 mm. (305 - 95) / 305 = 0.69X 44 mm x 0.69 = 30 mm - the fully illuminated circle.

At 0.67x, the CCDT67 will cover the chip of the ST10E. It can never cover the chip of an STL series camera or the newer large size digital SLR chips, because its clear aperture is no larger than their CCD chips.

0.75x Compression ratio for SBIG ST7/8/10 (without Color Filter Wheel or T-2 extensions), when used with refractors. Fully illuminated circle: 34mm"

The Optec reducer claims a "highly corrected" 18mm circle. On the next page it says compatible with Meade ACP scopes?? (And it's not a typo as it is repeated twice).

Has anyone used either of these devices with a DSLR (APS size sensor 22.7 x 15.1mm)?? I wonder if the quote from AP refers to full frame sensors? I hope to end up with a CCD camera, but that may be some time down the track??

Thanks
David T

[marki]

Originally Posted by DavidTrap

Has anyone used either of these devices with a DSLR (APS size sensor 22.7 x 15.1mm)?? I wonder if the quote from AP refers to full frame sensors? I hope to end up with a CCD camera, but that may be some time down the track??

Thanks
David T

I own both......my optec 0.7 is up for sale in the camera's section of the classifieds. Its imaging circle is too small for the KAF8300 (17.96 X 13.52 so diagonal is about 22.4mm) confirmed by OPTEC in an email (18 mm imaging circle, you will not be pleased witht e results...). It would be ok for small CCD's. You know how big the chip is on your DSLR, if you do the maths you will find your diagonal is 27.3mm......

Mark

[DavidTrap (David)]

Thanks for the reply Mark,

What scope are you using these on? Also, what sort of camera are you using?

I thought the small frame DSLR sensor might just be "fully illuminated", however, the reduction may be greater than .67x as the distance to the sensor might be greater, causing a smaller illuminated circle.

DT

[marki]

Originally Posted by DavidTrap

Thanks for the reply Mark,

What scope are you using these on? Also, what sort of camera are you using?

I thought the small frame DSLR sensor might just be "fully illuminated", however, the reduction may be greater than .67x as the distance to the sensor might be greater, causing a smaller illuminated circle.

DT

David I use these on a LX200R (same as the ACF). The KAF 8300 can be found in CCD camera,s from QHY, SBIG, Finger lakes, Orion, Atik, Starlight Xpress etc. I am using a QHY9 and the optec unit caused strong vignetting on the corners so was not good for this size chip. Best way to find out if it will work for your camera is to grab a compass and draw the fully illuminated field then try to fit the dimensions of your chip inside the circle. The AP needs to be 101mm from the chip to give 0.67 reduction and thus the 30mm imaging circle (actually 29 and a bit but close enough). The optec will not be suitable for the DSLR if your dimensions are correct....Email from optec;

"Thank you for your message. The ccd used in the QHY 9 camera has a 24mm diagonal. The NGUW 0.7x reducer will not cover this chip size, providing about an 18mm unvignetted image size. Unfortunately, I don’t think you would be satisfied with the resulting image".

Mark

[tonybarry (Tony)]

Thank you to all who have replied.

Peter, I have heard the same from other unverified sources, which indicate that the older SCT work well with the reducers, but the newer ACF do not work well with these reducers. Thank you for the Optec info, I shall keep it in mind.

Since this is the case, the question must be ... what kind of scopes are people using for large aperture, wide field imaging? Newts? It would seem the large aperture ACF scopes are not suitable, and have limited means to increase their field of view.

Regards,
Tony Barry

[DavidTrap (David)]

Not really sure where you are coming from Peter - the older SCTs need a flattener as well as a reducer - which is what you get when you buy the Meade .67 thingy.

I have seen several posts in various places suggesting the AP reducer for corrected SCTs (ie the ACF scopes). Certainly you don't want a flattener/reducer as the field is already flat.

Mark - do you have any photos you can post taken through your LX200R?

Thanks
David T

[PeterM]

Originally Posted by DavidTrap

Not really sure where you are coming from Peter - the older SCTs need a flattener as well as a reducer - which is what you get when you buy the Meade .67 thingy.

I have seen several posts in various places suggesting the AP reducer for corrected SCTs (ie the ACF scopes). Certainly you don't want a flattener/reducer as the field is already flat.

Mark - do you have any photos you can post taken through your LX200R?

Thanks
David T

Hi David,
Yep that is correct though I never suggested otherwise re the standard SCT as we were talking specifically about the ACF.
Optec have an F3 and an F5 reducer/flattener just as Meade have an F3.3-F5 and an F6.3 that will reduce and flatten for use with the standard SCT . And yes I have also heard very good reports about the AP reducers with the ACF scopes.
I now use the Optec F7 reducer (only) with my 12inch LX200R (ACF) and my Starlight Xpress SXVH9 ccd and this set up is ideal for the work I am doing.

On the Optec site they are referring to the ACF with the F7 - it actually notes ACF and the next page lists it as an ACP - it is a typo as I am not aware of any Meade ACP?

PeterM.

[tonybarry (Tony)]

Hello Peter,

Thank you for the clarifications. The 0.7x Optec unit would seem to be the only focal reducer then which does not over-flatten ACF optics. I would expect that Meade woud do something about this; selling the f/3.3 and f/6.3 reducer / flatteners for ACF scopes will not work (or else they won't work for the older SCTs which Meade still sell).

Does anyone know if Meade do in fact sell focal reducers just for ACF scopes?

Regards,
Tony Barry

[marki]

Originally Posted by DavidTrap

Certainly you don't want a flattener/reducer as the field is already flat.

Mark - do you have any photos you can post taken through your LX200R?

Thanks
David T

David the ACF field is not flat, there is still some curvature present. I only have roughies at the moment as I have been otherwise occupied. I have made simple tests to make sure the chip is fully illuminated and the reduction is about right. If you want to see some excellent pics using the Meade ACF/AP CCDT67 combo go to Basnut's website. He has taken some crackers using this combo and a ST10.

Peter the optec 0.7 reducer would be great with a SXVH9, small chips will work, it's just the larger versions that cause trouble.

The meade reducers do not work on the ACF, I have tried..... I would imagine the meade reducers would no longer serve the SCT crowd either as the imaging circle is way too small for modern cameras (e.g. 9mm for the F3.3). Best thing you can do is measure your chip and go hunting for something that will do the job. The fully illuminated circle is important and if it's not stated steer clear. These are just my thoughts after wasting a heap of money.



Mark