28 replies to this topic

[N2KEN]

The  Explore Scientific 0.7x Focal Reducer Corrector, aka Field Flattener - .7x Focal Reducer or FFFR, has no provision for mounting either 1.25" or 2" filters. Is this an issue for anyone else? How does ES suppose that customers attach filters when using their ES Field Flattener-Focal Reducer with a stock ES ED127APO, or other ES telescopes ?

 

Background and DIY Solution
I recently purchased an Explore Scientific ED127 APO refractor with stock 2" R&P focuser that I use for visual, EAA and to experiment with AP. I wanted to bring the ED127 down to F/5.25 for camera use, so I bought a used, complete and current model Explore Scientific 0.7x Focal Reducer Corrector. To bring my ZWO ASI224MC into focus I need two extension tubes on the focuser. The FFFR threads directly onto these extension tubes with an included adapter, and the camera attaches directly to T-threads at the other end. The two extension tubes were included with the ED127. Everything else is included with the FFFR to easily and securely attach a camera and use it with the stock 2" focuser and extension tubes. This set-up is 100% Explore Scientific except for the camera and is a very sturdy, rigid system. The FFFR kit also includes a 3" adapter for use with ES 152mm refractors.   

 

However, there's one major obstacle. There is no way to attach a 1.25" or 2" filter. There are no internal threads included inside the focuser, extension tubes or the FFFR. Since the 1.25" ZWO IR-cut filter for the 224MC normally threads into the 1.25" T-threaded nose piece, it cannot be used with the FFFR in the above configuration. Also, I saw no way to place my 2" L-Pro filter in the light path. 

 

I contacted ES Tech support to inquire about a solution to my filter mounting dilemma. According to the technician, they do not have an adapter or method of attaching filters. They offered to machine a flange with internal threads for a 2" filter, but this would cost me approximately $200. (ES ticket Reference: 556501-T8015). I declined and thanked them for their assistance.

 

Here are two suggested low-cost solutions for using 1.25" and 2" filters with the stock ED127 APO refractor, 2" stock R&P focuser, and ES FFFR.

 

1.25" Solution:
To attach a 1.25" filter to a stock Explore Scientific FFFR set-up, ScopeStuff has an adapter that works. This 1.25 Inch Filter Adapter for T-Thread Capture, #TFA1, places the filter neatly below the T-threads at the camera. It doesn't add any distance between the sensor and FFFR optics. It fits perfectly and there's adequate clearance so the filter will not hit the FFFR lens. There is no interference with the light path.

 

2" Solution:

Attaching a 2" filter is slightly more challenging. I used a ScopeStuff 2" M48 Filter Ring with Retainer, #TIFR, to place threads inside a spare extension tube. The inside diameter of the ES extension tube is just a hair over 2" (2.01" or 51.10mm). The OD of the filter ring is a hair under 2" (1.996" as per ScopeStuff). This M48 filter ring fits perfectly inside the extension tube. After removing some of the blackening inside the extension tube I carefully epoxied it inside the tube. A 2" filter sits nicely inside the tubes when threaded together.  This cuts down the light path from 2" to 1.7", which is the actual diameter of the filter glass. I haven't tested this yet in use, so I'm not sure if this will cause vignetting. The 224MC has a small 1/3" sensor, so probably not. With a large sensor it might cause vignetting.

 

The total cost of these two solutions is about $25 for the parts from ScopeStuff.  If you have a spare or damaged 2" filter, the ring might fit inside the extension tube to provide the threads for mounting a filter.  

 

I can't imagine why the Explore Scientific design engineers did not include any 1.25 or 2" filter threads or some type of filter adapter for their $299 Focal Reducer Corrector. If this was a mix and matched agglomeration of various parts from several vendors, I would understand the absence of filter threads. But this set-up is 100% pure, stock Explore Scientific and intended for use during AP.  I wasn't about to pay them $200 to custom fabricate an adapter to correct a missing feature in their product. 

 

Photos below

Edited by N2KEN, 08 February 2017 - 08:54 PM.

[N2KEN]

I didn't want to make the above post too long, so these are a few pics as an example of how to mount 1.25" and 2" filters in the FFFR. 

 

The FFFR threads onto the extension tubes. A 2" adapter is included in the kit from ES. The camera threads directly onto a T-Thread adapter at the other end. This is a very sturdy and rigid system.  My 1.25" and 2" filters are now snugly nestled inside this system for $25.

Mounting a 2" filter:

The M48 Filter Ring was epoxied inside an extension tube. A filter threads onto this ring. 

The extension tubes thread together without problems with the filter installed. 

 

Mounting a 1.25" filter:

See text in first post for a description

Edited by N2KEN, 08 February 2017 - 08:48 PM.

[tonyt]

I dropped a 2" filter inside the camera adapter which is only slightly larger than the filter - a piece or two of self adhesive felt keeps it in place. A threaded mount inside the adapter would have been nice though.

 

[DonBoy]

 

I didn't want to make the above post too long, so these are a few pics as an example of how to mount 1.25" and 2" filters in the FFFR. 

 

The FFFR threads onto the extension tubes. A 2" adapter is included in the kit from ES. The camera threads directly onto a T-Thread adapter at the other end. This is a very sturdy and rigid system.  My 1.25" and 2" filters are now snugly nestled inside this system for $25.

 

Mounting a 2" filter:

 

 

The M48 Filter Ring was epoxied inside an extension tube. A filter threads onto this ring. 

 

The extension tubes thread together without problems with the filter installed. 

 

 

Mounting a 1.25" filter:

See text in first post for a description

 

Ken, I have two adapters that I use with my 2" filter that I think would work.  The .7x FR/FF exits with a male M42 thread and screw that to a M42 female to male M48 adapter and screw that into front end of the 2" filter  which screws then onto a M48 female to M42 male adapter which then screws into the M42 thread of ASI224.  To do  1.25" just get one of those thin washers that fit inside of M42 spacers that hold a 1.25" filter which Scope stuff has and you can screw the .7xFR/FF into the ASI224 which you have the 1.25" filter and washer adapter laying in camera face, if that makes you uncomfortable first space out the ASI224 with a 5mm T2 spacer then lay in the 1.25" filter/washer adapter..   The two other adapters should be available from many sources on Ebay and possibly Amazon.

 

http://www.ebay.com/...CsAAOSwg3FUhRqZ

 

https://www.amazon.c...ale to m42 male

 

http://www.scopestuff.com/ss_tfa1.htm

Edited by DonBoy, 09 February 2017 - 05:33 PM.

[N2KEN]

Don,

The TFA1 "washer" is what I described in my post and is pictured above. That's the easiest way to add a 1.25 filter and works well.  For the M42 to M48 adapter method for adding a 2" filter, this would add additional space between the camera sensor and FFFR.  This distance is critical and adding adapters may degrade the image. 

Thanks for the comments,

Clear Skies  

_ _ . . .   . . . _ _

[tonyt]

Ken, the two dslr adapters pictured came with my reducer and it works well with my Canon 600D attached. Won't CCD's need extra spacers between the camera and reducer? 

 

[N2KEN]

Hi Tony,

Good point and thanks for the input. The present set-up using the ES CCD adapter in the kit gives about 25mm from the 224MC sensor to the lens of the FFFR.  I'm not sure whether the present spacing is optimum or not.   If my star shapes prove to be poor, I'll add more spacing to experiment.  My FFFR did not come with the Nikon and Cannon DSLR adapters - They look like they have significantly more spacing.  If someone uses this or a similar CMOS camera with the FFFR and CCD adapter, some input would be appreciated.

 

I've used the FFFR twice, but conditions were not good for taking meaningful images to judge star shapes and overall image quality. Darn clouds and wind . . .  I was able to focus and the images for several short exposures tentatively looked OK.  I'd really want to take some longer star exposures while guiding to examine star shapes across the field.  However, for EAA and casual AP experimentation this is not as critical as it will be for more serious AP work in the future.   

 

Out of curiosity I measured the spacing for the Hyperstar I use with my C9.25. It's about 55mm from the front of the Hyperstar lens to the sensor.  Not an apples to apples comparison. 

[N2KEN]

I've used the ES 0.7x Focal Reducer Corrector several times since my previous post. I experimented with various spacing, and 55mm provides the best image and the 0.7x focal reduction. A 20mm T2 extension and a Teleskop Service TST2VVAR variable extension (20.5-30mm) gave the needed spacing. The ZWO ASI224MC has 12.5mm spacing as per ZWO. 

 

Final configuration:

Edited by N2KEN, 07 March 2017 - 10:51 PM.

[Lead_Weight]

I've used the ES 0.7x Focal Reducer Corrector several times since my previous post. I experimented with various spacing, and 55mm provides the best image and the 0.7x focal reduction. A 20mm T2 extension and a Teleskop Service TST2VVAR variable extension (20.5-30mm) gave the needed spacing. The ZWO ASI224MC has 12.5mm spacing as per ZWO. 

 

Final configuration:

Thanks for this post. I'm sure i'll be in the same boat very soon. I just purchased the ES ED102 with focal reducer, and plan to do imaging with my ZWO ASI1600, and will definitely need the option of using filters. I was going to consider other reducer options but have not asked around yet. I'm also considering some Baader equipment behind the focuser as I really like their click lock stuff and currently use it on my SCT. Their equipment is all designed to accommodate threading filters and such on extensions tubes or eye piece locking mechanisms.

[N2KEN]

Thanks for this post. I'm sure i'll be in the same boat very soon. I just purchased the ES ED102 with focal reducer, and plan to do imaging with my ZWO ASI1600, and will definitely need the option of using filters. I was going to consider other reducer options but have not asked around yet. I'm also considering some Baader equipment behind the focuser as I really like their click lock stuff and currently use it on my SCT. Their equipment is all designed to accommodate threading filters and such on extensions tubes or eye piece locking mechanisms.

 

 

Explore Scientific was not very helpful with configuration information or a method to attach filters to their product. I was somewhat surprised at this gap in support since ES has a good reputation for being helpful.  This was a useful learning experience. The stock 2" R&P focuser on the ED127 is poor. It was very loose and needed extensive adjustment out of the box. How this passed QC is anyone's guess.  It does hold the FFFR and camera, but the image shifts slightly and wobbles during focusing and locking the focuser tube in place. I can see why upgrades are so common. The focuser will suffice for now. Aside from the below par focuser, I like the ED127 and my sample has good optics. Enjoy your ED102 / ASI1600 and hope you solve the filter challenge.  

[tonyt]

Ken I noticed that the serial number on your reducer is 344 and was presumably purchased in the US.

The serial number on my reducer is 27 and was purchased from England.

So ES either changed the included camera adapters somewhere along the production series or different adapters are sold in Europe than in the US.

 

It's a shame ES doesn't offer a variety of camera adapters and focuser adapters to suit their reducer. An adapter for the 3" FT focuser is an obvious choice for owners upgrading the supplied focuser. 

[N2KEN]

Tonyt,

Adapters for the ES Focal Reducer Corrector are available from both Starlight and Moonlite for their respective focuser lines. Several posts have mentioned the purchase of these adapters. In the past I've seen the Nikon and Canon adapters included on the European sites, but not on the U.S. site. I guess there is an associated marketing strategy or sales restriction that guides the back office masterminds at ES Headquarters.  I bought my FFFR used at a good price, and I'm quite pleased with the optical quality.    

[tonyt]

So I guess if dslr adaptors are needed buy in Europe, otherwise buy from the US - handy to be aware of. Strange marketing though.  

[Lead_Weight]

 

Thanks for this post. I'm sure i'll be in the same boat very soon. I just purchased the ES ED102 with focal reducer, and plan to do imaging with my ZWO ASI1600, and will definitely need the option of using filters. I was going to consider other reducer options but have not asked around yet. I'm also considering some Baader equipment behind the focuser as I really like their click lock stuff and currently use it on my SCT. Their equipment is all designed to accommodate threading filters and such on extensions tubes or eye piece locking mechanisms.

 

 

Explore Scientific was not very helpful with configuration information or a method to attach filters to their product. I was somewhat surprised at this gap in support since ES has a good reputation for being helpful.  This was a useful learning experience. The stock 2" R&P focuser on the ED127 is poor. It was very loose and needed extensive adjustment out of the box. How this passed QC is anyone's guess.  It does hold the FFFR and camera, but the image shifts slightly and wobbles during focusing and locking the focuser tube in place. I can see why upgrades are so common. The focuser will suffice for now. Aside from the below par focuser, I like the ED127 and my sample has good optics. Enjoy your ED102 / ASI1600 and hope you solve the filter challenge.  

 

Managed to get all the equipment together tonight and connect it together. Looks like my camera has a screw off plate where you can place a filter right in front of the sensor, so it looks like I don't have the same issue. Here's what the base of my camera looks like where the filter goes (plate with 4 screws).

[Lead_Weight]

I want to reiterate my thanks to Ken for testing the FFFR to find the best back focus distance. Plus, his images with labels were invaluable for my own knowledge and info. While I don't have the same issue he had with regards to fitting the filter. I've been planning on how to achieve proper back focus with my particular setup, and hope to post here with images as soon as the equipment comes in.

 

From the FFFR Back, my goal was to introduce a Baader click lock 2" holder so I could easily rotate my ASI1600 camera to orient it for the best image possible of my subject. To achieve the 55mm back focus I've ordered the following parts:

 

Teleskop 3mm extension + Teleskop 8mm extension + Baader T2 2" Clicklock 37mm. Then add to that the .5mm space from glass to edge of FFFR and my 6.5mm space to sensor on the camera itself and that should equal 55mm.

[siriusarcher]

I've been watching this thread too, add echo my thanks to Ken for the excellent information about connecting the FF/FR and achieving the proper back focus. I also recently bought this device ("holy hand grenade" as someone put it). It seems to be working well, but I'm hoping to do a test of this FF/FR on a large format camera chip (36mm by 36mm) to ascertain the degree to which it flattens the field, and perhaps to answer the question of what size of sensor the 127mm (and possibly the 152mm) ES ED scopes can handle. If anyone following this thread already has done this test and has information, do tell! Probably warrants a new discussion topic.

[Lead_Weight]

I want to reiterate my thanks to Ken for testing the FFFR to find the best back focus distance. Plus, his images with labels were invaluable for my own knowledge and info. While I don't have the same issue he had with regards to fitting the filter. I've been planning on how to achieve proper back focus with my particular setup, and hope to post here with images as soon as the equipment comes in.

 

From the FFFR Back, my goal was to introduce a Baader click lock 2" holder so I could easily rotate my ASI1600 camera to orient it for the best image possible of my subject. To achieve the 55mm back focus I've ordered the following parts:

 

Teleskop 3mm extension + Teleskop 8mm extension + Baader T2 2" Clicklock 37mm. Then add to that the .5mm space from glass to edge of FFFR and my 6.5mm space to sensor on the camera itself and that should equal 55mm.

I don't have great news for myself and other ES102" owners with the ES FFFR. After discussing with ES support, I'm not going to be able to reach focus, and they've offered me a refund and return. Luckily all the equipment I've ordered for the image train should work as 55mm is fairly standard back focus distance for most reducers. I'm now on the hunt for a new reducer/flattener.

[EverettQ]

Mine is working perfectly with the ZWO OAG, ZWO EFW, and ZWO ASI1600MM-Cool and ZWO ASI120MM-S 

 

Here's a video for more information regarding focus and spacers https://www.youtube....rDaReVEBc&t=25s

Edited by EverettQ, 24 April 2017 - 09:40 PM.

[KevinS]

You want 55mm from the shoulder to sensor.

Here's mine with an Orion TOAG almost identical to Vostok 1's

 

Edited by KevinS, 20 March 2018 - 08:19 AM.

[View2]

Also, you can put a filter over the sensor in the camera with an adapter

[Carl N]

I know old thread, but I'm exploring the 3" FF/FR being discussed for an AT152EDT coming next week.

Did the OP ever solve his filter problem?
I see several options. One, with the CCD adapter, you have enough back focus for a filter wheel and remove some spacer. Or, for a DSLR where you need the filter in front of the FF, put a Filter Drawer I to the train. Gerd Neuman filter drawer <-- Google

[DonBoy]

One of my solutions with the ES .7xFR/FF is to use a M42/M48 adapter attached to the back of the reducer's male M42 thread and then the M48 filter and then a M48 to M42 extension(16.5mm ZWO) + balance of M42 extensions to make up 55mm back focus.

Edited by DonBoy, 16 November 2018 - 10:52 PM.

[EverettQ]

Here's just an update of mine

 

[NWAAstronomer]

The current version of the 2-inch adapter for the FFFR is threaded to accept 2-inch filters.

Here is a link: https://explorescien...ducts/2-adapter

The unit in the photo shows machine milling; however, the current version has a smooth interior barrel with a quart-inch of thread.

Edited by NWAAstronomer, 30 November 2018 - 01:13 PM.

[thekubiaks]

Here's just an update of mine

 

Thank you EverettQ for this picture, I wasted four hours trying to get my ED 127 with this ES .7x focal reducer to work with the ASI294MC and 1600MM.   Everything put out by ZWO says 55mm back focus but whether the correct measurement point was the back of the focal reducer or the focal reducer lens wasn't mentioned.  Now my problem is solved.  I owe you a beer. btw, the focal reducer back edge to lens is 9mm

Edited by thekubiaks, 20 December 2019 - 12:58 AM.